Provided by: spamassassin_4.0.0-8ubuntu5_all 
NAME
Mail::SpamAssassin::Plugin::TxRep - Normalize scores with sender reputation records
SYNOPSIS
The TxRep (Reputation) plugin is designed as an improved replacement of the AWL (Auto-
Welcomelist) plugin. It adjusts the final message spam score by looking up and taking in
consideration the reputation of the sender.
To try TxRep out, you have to first disable the AWL plugin (if enabled), and back up its
database. AWL is loaded in v310.pre and can be disabled by commenting out the loadplugin
line:
# loadplugin Mail::SpamAssassin::Plugin::AWL
When AWL is not disabled, TxRep will refuse to run.
TxRep should be enabled by uncommenting the following line in v341.pre:
loadplugin Mail::SpamAssassin::Plugin::TxRep
Use the supplied 60_txreputation.cf file or add these lines to a .cf file:
header TXREP eval:check_senders_reputation()
describe TXREP Score normalizing based on sender's reputation
tflags TXREP userconf noautolearn
priority TXREP 1000
DESCRIPTION
This plugin is intended to replace the former AWL - AutoWelcomeList. Although the concept
and the scope differ, the purpose remains the same - the normalizing of spam score results
based on previous sender's history. The name was intentionally changed from "whitelist" to
"reputation" to avoid any confusion, since the result score can be adjusted in both
directions.
The TxRep plugin keeps track of the average SpamAssassin score for senders. Senders are
tracked using multiple identificators, or their combinations: the From: email address,
the originating IP and/or an originating block of IPs, sender's domain name, the DKIM
signature, and the HELO name. TxRep then uses the average score to reduce the variability
in scoring from message to message, and modifies the final score by pushing the result
towards the historical average. This improves the accuracy of filtering for most email.
In comparison with the original AWL plugin, several conceptual changes were implemented in
TxRep:
1. Scoring - at AWL, although it tracks the number of messages received from each
respective sender, when calculating the corrective score at a new message, it does not
take it in count in any way. So for example a sender who previously sent a single ham
message with the score of -5, and then sends a second one with the score of +10, AWL will
issue a corrective score bringing the score towards the -5. With the default
"auto_welcomelist_factor" of 0.5, the resulting score would be only 2.5. And it would be
exactly the same even if the sender previously sent 1,000 messages with the average of -5.
TxRep tries to take the maximal advantage of the collected data, and adjusts the final
score not only with the mean reputation score stored in the database, but also respecting
the number of messages already seen from the sender. You can see the exact formula in the
section ""txrep_factor"".
2. Learning - AWL ignores any spam/ham learning. In fact it acts against it, which often
leads to a frustrating situation, where a user repeatedly tags all messages of a given
sender as spam (resp. ham), but at any new message from the sender, AWL will adjust the
score of the message back to the historical average which does not include the learned
scores. This is now changed at TxRep, and every spam/ham learning will be recorded in the
reputation database, and hence taken in consideration at future email from the respective
sender. See the section "LEARNING SPAM / HAM" for more details.
3. Auto-Learning - in certain situations SpamAssassin may declare a message an obvious
spam resp. ham, and launch the auto-learning process, so that the message can be re-
evaluated. AWL, by design, did not perform any auto-learning adjustments. This plugin will
readjust the stored reputation by the value defined by ""txrep_learn_penalty"" resp.
""txrep_learn_bonus"". Auto-learning score thresholds may be tuned, or the auto-learning
completely disabled, through the setting ""txrep_autolearn"".
4. Relearning - messages that were wrongly learned or auto-learned, can be relearned. Old
reputations are removed from the database, and new ones added instead of them. The
relearning works better when message tracking is enabled through the
""txrep_track_messages"" option. Without it, the relearned score is simply added to the
reputation, without removing the old ones.
5. Aging - with AWL, any historical record of given sender has the same weight. It means
that changes in senders behavior, or modified SA rules may take long time, or be virtually
negated by the AWL normalization, especially at senders with high count of past messages,
and low recent frequency. It also turns to be particularly counterproductive when the
administrator detects new patterns in certain messages, and applies new rules to better
tag such messages as spam or ham. AWL will practically eliminate the effect of the new
rules, by adjusting the score back towards the (wrong) historical average. Only setting
the "auto_welcomelist_factor" lower would help, but in the same time it would also reduce
the overall impact of AWL, and put doubts on its purpose. TxRep, besides the
""txrep_factor"" (replacement of the "auto_welcomelist_factor"), introduces also the
""txrep_dilution_factor"" to help coping with this issue by progressively reducing the
impact of past records. More details can be found in the description of the factor below.
6. Blocklisting and Welcomelisting - when a welcomelisting or blocklisting was requested
through SpamAssassin's API, AWL adjusts the historical total score of the plain email
address without IP (and deleted records bound to an IP), but since during the reception
new records with IP will be added, the blocklisted entry would cease acting during
scanning. TxRep always uses the record of the plain email address without IP together with
the one bound to an IP address, DKIM signature, or SPF pass (unless the weight factor for
the EMAIL reputation is set to zero). AWL uses the score of 100 (resp. -100) for the
blocklisting (resp. welcomelisting) purposes. TxRep increases the value proportionally to
the weight factor of the EMAIL reputation. It is explained in details in the section "
WELCOMELISTING" in BLOCKLISTING . TxRep can blocklist or welcomelist also IP addresses,
domain names, and dotless HELO names.
7. Sender Identification - AWL identifies a sender on the basis of the email address used,
and the originating IP address (better told its part defined by the mask setting). The
main purpose of this measure is to avoid assigning false good scores to spammers who spoof
known email addresses. The disadvantage appears at senders who send from frequently
changing locations or even when connecting through dynamical IP addresses that are not
within the block defined by the mask setting. Their score is difficult or sometimes
impossible to track. Another disadvantage is, for example, at a spammer persistently
sending spam from the same IP address, just under different email addresses. AWL will not
find his previous scores, unless he reuses the same email address again. TxRep uses
several identificators, and creates separate database entries for each of them. It tracks
not only the email/IP address combination like AWL, but also the standalone email address
(regardless of the originating IP), the standalone IP (regardless of email address used),
the domain name of the email address, the DKIM signature, and the HELO name of the
connecting PC. The influence of each individual identificator may be tuned up with the
help of weight factors described in the section "REPUTATION WEIGHTS".
8. Message Tracking - TxRep (optionally) keeps track of already scanned and/or learned
message ID's. This is useful for avoiding to strengthen the reputation score by simply
rescanning or relearning the same message multiple times. In the same time it also allows
the proper relearning of once wrongly learned messages, or relearning them after the learn
penalty or bonus were changed. See the option ""txrep_track_messages"".
9. User and Global Storages - usually it is recommended to use the per-user setup of
SpamAssassin, because each user may have quite different requirements, and may receive
quite different sort of email. Especially when using the Bayesian and AWL plugins, the
efficiency is much better when SpamAssassin is learned spam and ham separately for each
user. However, the disadvantage is that senders and emails already learned many times by
different users, will need to be relearned without any recognized history, anytime they
arrive to another user. TxRep uses the advantages of both systems. It can use dual
storages: the global common storage, where all email processed by SpamAssassin is
recorded, and a local storage separate for each user, with reputation data from his email
only. See more details at the setting ""txrep_user2global_ratio"".
10. Outbound Welcomelisting - when a local user sends messages to an email address, we
assume that he needs to see the eventual answer too, hence the recipient's address should
be welcomelisted. When SpamAssassin is used for scanning outgoing email too, when local
users use the SMTP server where SA is installed, for sending email, and when internal
networks are defined, TxREP will improve the reputation of all 'To:' and 'CC' addresses
from messages originating in the internal networks. Details can be found at the setting
""txrep_welcomelist_out"".
Both plugins (AWL and TxREP) cannot coexist. It is necessary to disable the AWL to allow
TxRep running. TxRep reuses the database handling of the original AWL module, and some its
parameters bound to the database handler modules. By default, TxRep creates its own
database, but the original auto-welcomelist can be reused as a starting point. The AWL
database can be renamed to the name defined in TxRep settings, and TxRep will start using
it. The original auto-welcomelist database has to be backed up, to allow switching back to
the original state.
The spamassassin/Plugin/TxRep.pm file replaces both spamassassin/Plugin/AWL.pm and
spamassassin/AutoWelcomelist.pm. Another two AWL files, spamassassin/DBBasedAddrList.pm
and spamassassin/SQLBasedAddrList.pm are still needed.
TEMPLATE TAGS
This plugin module adds the following "tags" that can be used as placeholders in certain
options. See Mail::SpamAssassin::Conf for more information on TEMPLATE TAGS.
_TXREPXXXY_ TXREP modifier
_TXREPXXXYMEAN_ Mean score on which TXREP modification is based
_TXREPXXXYCOUNT_ Number of messages on which TXREP modification is based
_TXREPXXXYPRESCORE_ Score before TXREP
_TXREPXXXYUNKNOWN_ New sender (not found in the TXREP list)
The XXX part of the tag takes the form of one of the following IDs, depending on the
reputation checked: EMAIL, EMAILIP, IP, DOMAIN, or HELO. The Y appendix ID is used only in
the case of dual storage, and takes the form of either U (for user storage reputations),
or G (for global storage reputations).
USER PREFERENCES
The following options can be used in both site-wide ("local.cf") and user-specific
("user_prefs") configuration files to customize how SpamAssassin handles incoming email
messages.
use_txrep
0 | 1 (default: 0)
Whether to use TxRep reputation system. TxRep tracks the long-term average score for
each sender and then shifts the score of new messages toward that long-term average.
This can increase or decrease the score for messages, depending on the long-term
behavior of the particular correspondent.
Note that certain tests are ignored when determining the final message score:
- rules with tflags set to 'noautolearn'
txrep_factor
range [0..1] (default: 0.5)
How much towards the long-term mean for the sender to regress a message. Basically,
the algorithm is to track the long-term total score and the count of messages for the
sender ("total" and "count"), and then once we have otherwise fully calculated the
score for this message ("score"), we calculate the final score for the message as:
finalscore = score + factor * (total + score)/(count + 1)
So if "factor" = 0.5, then we'll move to half way between the calculated score and the
new mean value. If "factor" = 0.3, then we'll move about 1/3 of the way from the
score toward the mean. "factor" = 1 means use the long-term mean including also the
new unadjusted score; "factor" = 0 mean just use the calculated score, disabling so
the score averaging, though still recording the reputation to the database.
txrep_dilution_factor
range [0.7..1.0] (default: 0.98)
At any new email from given sender, the historical reputation records are "diluted",
or "watered down" by certain fraction given by this factor. It means that the
influence of old records will progressively diminish with every new message from given
sender. This is important to allow a more flexible handling of changes in sender's
behavior, or new improvements or changes of local SA rules.
Without any dilution expiry (dilution factor set to 1), the new message score is
simply add to the total score of given sender in the reputation database. When
dilution is used (factor < 1), the impact of the historical reputation average is
reduced by the factor before calculating the new average, which in turn is then used
to adjust the new total score to be stored in the database.
newtotal = (oldcount + 1) * (newscore + dilution * oldtotal) / (dilution * oldcount + 1)
In other words, it means that the older a message is, the less and less impact on the
new average its original spam score has. For example if we set the factor to 0.9
(meaning dilution by 10%), the score of the new message will be recorded to its 100%,
the last score of the same sender to 90%, the second last to 81% (0.9 * 0.9 = 0.81),
and for example the 10th last message just to 35%.
At stable systems, we recommend keeping the factor close to 1 (but still lower than
1). At systems where SA rules tuning and spam learning is still in progress, lower
factors will help the reputation to quicker adapt any modifications. In the same time,
it will also reduce the impact of the historical reputation though.
txrep_learn_penalty
range [0..200] (default: 20)
When SpamAssassin is trained a SPAM message, the given penalty score will be added to
the total reputation score of the sender, regardless of the real spam score. The
impact of the penalty will be the smaller the higher is the number of messages that
the sender already has in the TxRep database.
txrep_learn_bonus
range [0..200] (default: 20)
When SpamAssassin is trained a HAM message, the given penalty score will be deduced
from the total reputation score of the sender, regardless of the real spam score. The
impact of the penalty will be the smaller the higher is the number of messages that
the sender already has in the TxRep database.
txrep_autolearn
range [0..5] (default: 0)
When SpamAssassin declares a message a clear spam resp. ham during the message scan,
and launches the auto-learn process, sender reputation scores of given message will be
adjusted by the value of the option ""txrep_learn_penalty"", resp. the
""txrep_learn_bonus"" in the same way as during the manual learning. Value 0 at this
option disables the auto-learn reputation adjustment - only the score calculated
before the auto-learn will be stored to the reputation database.
txrep_track_messages
0 | 1 (default: 1)
Whether TxRep should keep track of already scanned and/or learned messages. When
enabled, an additional record in the reputation database will be created to avoid
false score adjustments due to repeated scanning of the same message, and to allow
proper relearning of messages that were either previously wrongly learned, or need to
be relearned after modifying the learn penalty or bonus.
txrep_welcomelist_out
range [0..200] (default: 10)
Previously txrep_whitelist_out which will work interchangeably until 4.1.
When the value of this setting is greater than zero, recipients of messages sent from
within the internal networks will be welcomelisted through improving their total
reputation score with the number of points defined by this setting. Since the IP
address and other sender identificators are not known when sending the email, only the
reputation of the standalone email is being welcomelisted. The domain name is
intentionally also left unaffected. The outbound welcomelisting can only work when
SpamAssassin is set up to scan also outgoing email, when local users use the SMTP
server for sending email, and when "internal_networks" are defined in SpamAssassin
configuration. The improving of the reputation happens at every message sent from
internal networks, so the more messages is being sent to the recipient, the better
reputation his email address will have.
txrep_ipv4_mask_len
range [0..32] (default: 16)
The AWL database keeps only the specified number of most-significant bits of an IPv4
address in its fields, so that different individual IP addresses within a subnet
belonging to the same owner are managed under a single database record. As we have no
information available on the allocated address ranges of senders, this CIDR mask
length is only an approximation. The default is 16 bits, corresponding to a former
class B. Increase the number if a finer granularity is desired, e.g. to 24 (class C)
or 32. A value 0 is allowed but is not particularly useful, as it would treat the
whole internet as a single organization. The number need not be a multiple of 8, any
split is allowed.
txrep_ipv6_mask_len
range [0..128] (default: 48)
The AWL database keeps only the specified number of most-significant bits of an IPv6
address in its fields, so that different individual IP addresses within a subnet
belonging to the same owner are managed under a single database record. As we have no
information available on the allocated address ranges of senders, this CIDR mask
length is only an approximation. The default is 48 bits, corresponding to an address
range commonly allocated to individual (smaller) organizations. Increase the number
for a finer granularity, e.g. to 64 or 96 or 128, or decrease for wider ranges, e.g.
32. A value 0 is allowed but is not particularly useful, as it would treat the whole
internet as a single organization. The number need not be a multiple of 4, any split
is allowed.
user_awl_sql_override_username
string (default: undefined)
Used by the SQLBasedAddrList storage implementation.
If this option is set the SQLBasedAddrList module will override the set username with
the value given. This can be useful for implementing global or group based TxRep
databases.
txrep_user2global_ratio
range [0..10] (default: 0)
When the option txrep_user2global_ratio is set to a value greater than zero, and if
the server configuration allows it, two data storages will be used - user and global
(server-wide) storages.
User storage keeps only senders who send messages to the respective recipient, and
will reflect also the corrected/learned scores, when some messages are marked by the
user as spam or ham, or when the sender is welcomelisted or blocklisted through the
API of SpamAssassin.
Global storage keeps the reputation data of all messages processed by SpamAssassin
with their spam scores and spam/ham learning data from all users on the server.
Hence, the module will return a reputation value even at senders not known to the
current recipient, as long as he already sent email to anyone else on the server.
The value of the txrep_user2global_ratio parameter controls the impact of each of the
two reputations. When equal to 1, both the global and the user score will have the
same impact on the result. When set to 2, the reputation taken from the user storage
will have twice the impact of the global value. The final value of the TXREP tag will
be calculated as follows:
total = ( ratio * user + global ) / ( ratio + 1 )
When no reputation is found in the user storage, and a global reputation is available,
the global storage is used fully, without applying the ratio.
When the ratio is set to zero, only the default storage will be used. And it then
depends whether you use the global, or the local user storage by default, which in
turn is controlled either by the parameter user_awl_sql_override_username (in case of
SQL storage), or the "/auto_welcomelist_path" parameter (in case of Berkeley
database).
When this dual storage is enabled, and no global storage is defined by the above
mentioned parameters for the Berkeley or SQL databases, TxRep will attempt to use a
generic storage - user 'GLOBAL' in case of SQL, and in the case of Berkeley database
it uses the path defined by '__local_state_dir__/tx-reputation', which typically
renders into /var/db/spamassassin/tx-reputation. When the default storages are not
available, or are not writable, you would have to set the global storage with the help
of the "user_awl_sql_override_username" resp. "auto_welcomelist_path settings".
Please note that some SpamAssassin installations run always under the same user ID. In
such case it is pointless enabling the dual storage, because it would maximally lead
to two identical global storages in different locations.
This feature is disabled by default.
auto_welcomelist_distinguish_signed (default: 1 - enabled)
Previously auto_welcomelist_distinguish_signed which will work interchangeably until
4.1.
Used by the SQLBasedAddrList storage implementation.
If this option is set the SQLBasedAddrList module will keep separate database entries
for DKIM-validated e-mail addresses and for non-validated ones. Without this option,
or for domains that do not use a DKIM signature, the reputation of legitimate email
can get mixed with the reputation of forgeries. A pre-requisite when setting this
option is that a field txrep.signedby exists in a SQL table, otherwise SQL operations
will fail. A DKIM plugin must also be enabled in order for this option to take
effect. This option is highly recommended. Unless you are using a pre-3.3.0 database
schema and cannot upgrade, there is no reason to disable this option. If you are
upgrading from AWL and using a pre-3.3.0 schema, the txrep.signedby column will not
exist. It is recommended that you add this column, but if that is not possible you
must set this option to 0 to avoid SQL errors.
txrep_spf
0 | 1 (default: 1)
When enabled, TxRep will treat any IP address using a given email address as the same
authorized identity, and will not associate any IP address with it. (The same happens
with valid DKIM signatures. No option available for DKIM).
Note: at domains that define the useless SPF +all (pass all), no IP would be ever
associated with the email address, and all addresses (incl. the forged ones) would be
treated as coming from the authorized source. However, such domains are hopefully
rare, and ask for this kind of treatment anyway.
REPUTATION WEIGHTS
The overall reputation of the sender comprises several elements:
1) The reputation of the 'From' email address bound to the originating IP address fraction
(see the mask parameters for details)
2) The reputation of the 'From' email address alone (regardless the IP address being
currently used)
3) The reputation of the domain name of the 'From' email address
4) The reputation of the originating IP address, regardless of sender's email address
5) The reputation of the HELO name of the originating computer (if available)
Each of these partial reputations is weighted with the help of these parameters, and the
overall reputation is calculation as the sum of the individual reputations divided by the
sum of all their weights:
sender_reputation = weight_email * rep_email +
weight_email_ip * rep_email_ip +
weight_domain * rep_domain +
weight_ip * rep_ip +
weight_helo * rep_helo
You can disable the individual partial reputations by setting their respective weight to
zero. This will also reduce the size of the database, since each partial reputation
requires a separate entry in the database table. Disabling some of the partial reputations
in this way may also help with the performance on busy servers, because the respective
database lookups and processing will be skipped too.
txrep_weight_email
range [0..10] (default: 3)
This weight factor controls the influence of the reputation of the standalone email
address, regardless of the originating IP address. When adjusting the weight, you need
to keep on mind that an email address can be easily spoofed, and hence spammers can
use 'from' email addresses belonging to senders with good reputation. From this point
of view, the email address bound to the originating IP address is a more reliable
indicator for the overall reputation.
On the other hand, some reputable senders may be sending from a bigger number of IP
addresses, so looking for the reputation of the standalone email address without
regarding the originating IP has some sense too.
We recommend using a relatively low value for this partial reputation.
txrep_weight_email_ip
range [0..10] (default: 10)
This is the standard reputation used in the same way as it was by the original AWL
plugin. Each sender's email address is bound to the originating IP, or its part as
defined by the txrep_ipv4_mask_len or txrep_ipv6_mask_len parameters.
At a user sending from multiple locations, diverse mail servers, or from a dynamic IP
range out of the masked block, his email address will have a separate reputation value
for each of the different (partial) IP addresses.
When the option auto_welcomelist_distinguish_signed is enabled, in contrary to the
original AWL module, TxRep does not record the IP address when DKIM signature is
detected. The email address is then not bound to any IP address, but rather just to
the DKIM signature, since it is considered that it authenticates the sender more
reliably than the IP address (which can also vary).
This is by design the most relevant reputation, and its weight should be kept high.
txrep_weight_domain
range [0..10] (default: 2)
Some spammers may use always their real domain name in the email address, just with
multiple or changing local parts. This reputation will record the spam scores of all
messages send from the respective domain, regardless of the local part (user name)
used.
Similarly as with the email_ip reputation, the domain reputation is also bound to the
originating address (or a masked block, if mask parameters used). It avoids giving
false reputation based on spoofed email addresses.
In case of a DKIM signature detected, the signature signer is used instead of the
domain name extracted from the email address. It is considered that the signing
authority is responsible for sending email of any domain name, hence the same
reputation applies here.
The domain reputation will give relevant picture about the owner of the domain in case
of small servers, or corporation with strict policies, but will be less relevant for
freemailers like Gmail, Hotmail, and similar, because both ham and spam may be sent by
their users.
The default value is set relatively low. Higher weight values may be useful, but we
recommend caution and observing the scores before increasing it.
txrep_weight_ip
range [0..10] (default: 4)
Spammers can send through the same relay (incl. compromised hosts) under a multitude
of email addresses. This is the exact case when the IP reputation can help. This
reputation is a kind of a local RBL.
The weight is set by default lower than for the email_IP reputation, because there may
be cases when the same IP address hosts both spammers and acceptable senders (for
example the marketing department of a company sends you spam, but you still need to
get messages from their billing address).
txrep_weight_helo
range [0..10] (default: 0.5)
Big number of spam messages come from compromised hosts, often personal computers, or
top-boxes. Their NetBIOS names are usually used as the HELO name when connecting to
your mail server. Some of the names are pretty generic and hence may be shared by a
big number of hosts, but often the names are quite unique and may be a good indicator
for detecting a spammer, despite that he uses different email and IP addresses (spam
can come also from portable devices).
No IP address is bound to the HELO name when stored to the reputation database. This
is intentional, and despite the possibility that numerous devices may share some of
the HELO names.
This option is still considered experimental, hence the low weight value, but after
some testing it could be likely at least slightly increased.
ADMINISTRATOR SETTINGS
These settings differ from the ones above, in that they are considered 'more privileged'
-- even more than the ones in the PRIVILEGED SETTINGS section. No matter what
"allow_user_rules" is set to, these can never be set from a user's "user_prefs" file.
txrep_factory module
(default: Mail::SpamAssassin::DBBasedAddrList)
Select alternative database factory module for the TxRep database.
auto_welcomelist_path /path/filename
(default: ~/.spamassassin/tx-reputation)
Previously auto_whitelist_path which will work interchangeably until 4.1.
This is the TxRep directory and filename. By default, each user has their own
reputation database in their "~/.spamassassin" directory with mode 0700. For system-
wide SpamAssassin use, you may want to share this across all users.
auto_welcomelist_db_modules Module ...
(default: see below)
Previously auto_whitelist_db_modules which will work interchangeably until 4.1.
What database modules should be used for the TxRep storage database file. The first
named module that can be loaded from the Perl include path will be used. The format
is:
PreferredModuleName SecondBest ThirdBest ...
ie. a space-separated list of Perl module names. The default is:
DB_File GDBM_File SDBM_File
NDBM_File is not supported (see SpamAssassin bug 4353).
auto_welcomelist_file_mode
(default: 0700)
Previously auto_whitelist_file_mode which will work interchangeably until 4.1.
The file mode bits used for the TxRep directory or file.
Make sure you specify this using the 'x' mode bits set, as it may also be used to
create directories. However, if a file is created, the resulting file will not have
any execute bits set (the umask is set to 0111).
user_awl_dsn DBI:databasetype:databasename:hostname:port
Used by the SQLBasedAddrList storage implementation.
This will set the DSN used to connect. Example: "DBI:mysql:spamassassin:localhost"
user_awl_sql_username username
Used by the SQLBasedAddrList storage implementation.
The authorized username to connect to the above DSN.
user_awl_sql_password password
Used by the SQLBasedAddrList storage implementation.
The password for the database username, for the above DSN.
user_awl_sql_table tablename
(default: txrep)
Used by the SQLBasedAddrList storage implementation.
The table name where reputation is to be stored in, for the above DSN.
BLOCKLISTING / WELCOMELISTING
When asked by SpamAssassin to blocklist or welcomelist a user, the TxRep plugin adds a
score of 100 (for blocklisting) or -100 (for welcomelisting) to the given sender's email
address. At a plain address without any IP address, the value is multiplied by the ratio
of total reputation weight to the EMAIL reputation weight to account for the reduced
impact of the standalone EMAIL reputation when calculating the overall reputation.
total_weight = weight_email + weight_email_ip + weight_domain + weight_ip + weight_helo
blocklisted_reputation = 100 * total_weight / weight_email
When a standalone email address is blocklisted/welcomelisted, all records of the email
address bound to an IP address, DKIM signature, or a SPF pass will be removed from the
database, and only the standalone record is kept.
Besides blocklisting/welcomelisting of standalone email addresses, the same method may be
used also for blocklisting/welcomelisting of IP addresses, domain names, and HELO names
(only dotless Netbios HELO names can be used).
When welcomelisting/blocklisting an email address or domain name, you can bind them to a
specified DKIM signature or SPF record by appending the DKIM signing domain or the tag
'spf' after the ID in the following way:
spamassassin --add-addr-to-blocklist=spamming.biz,spf
spamassassin --add-addr-to-welcomelist=friend@good.org,good.org
When a message contains both a DKIM signature and an SPF pass, the DKIM signature takes
the priority, so the record bound to the 'spf' tag won't be checked. Only email addresses
and domains can be bound to DKIM or SPF. Records of IP addresses and HELO names are
always without DKIM/SPF.
In case of dual storage, the block/welcomelisting is performed only in the default
storage.
REPUTATION LOGICS
1. The most significant sender identificator is equally as at AWL, the
combination of the email address and the originating IP address, resp.
its part defined by the IPv4 resp. IPv6 mask setting.
2. No IP checking for standalone EMAIL address reputation
3. No signature checking for IP reputation, and for HELO name reputation
4. The EMAIL_IP weight, and not the standalone EMAIL weight is used when
no IP address is available (EMAIL_IP is the main indicator, and has
the highest weight)
5. No IP checking at signed emails (signature authenticates the email
instead of the IP address)
6. No IP checking at SPF pass (we assume the domain owner is responsible
for all IP's he authorizes to send from, hence we use the same identity
for all of them)
7. No signature used for standalone EMAIL reputation (would be redundant,
since no IP is used at signed EMAIL_IP reputation, and we would store
two identical hits)
8. When available, the DKIM signer is used instead of the domain name for
the DOMAIN reputation
9. No IP and no signature used for HELO reputation (despite the possibility
of the possible existence of multiple computers with the same HELO)
10. The full (unmasked IP) address is used (in the address field, instead the
IP field) for the standalone IP reputation
LEARNING SPAM / HAM
When SpamAssassin is told to learn (or relearn) a given message as spam or ham, all
reputations relevant to the message (email, email_ip, domain, ip, helo) in both global and
user storages will be updated using the "txrep_learn_penalty" respectively the
"rxrep_learn_bonus" values. The new reputation of given sender property (email,
domain,...) will be the respective result of one of the following formulas:
new_reputation = old_reputation + learn_penalty
new_reputation = old_reputation - learn_bonus
The TxRep plugin currently does track each message individually, hence it does not detect
when you learn the message repeatedly. It will add/subtract the penalty/bonus score each
time the message is fed to the spam learner.
OPTIMIZING TXREP
TxRep can be optimized for speed and simplicity, or for the precision in assigning the
reputation scores.
First of all TxRep can be quickly disabled and re-enabled through the option
""use_txrep"". It can be done globally, or individually in each respective "user_prefs".
Disabling TxRep will not destroy the database, so it can be re-enabled any time later
again.
On many systems, SQL-based storage may perform faster than the default Berkeley DB
storage, so you should consider setting it up.
Then there are multiple settings that can reduce the number of records stored in the
database, hence reducing the size of the storage, and also the processing time:
1. Setting ""txrep_user2global_ratio"" to zero will disable the dual storage, halving so
the disk space requirements, and the processing times of this plugin.
2. You can disable all but one of the "REPUTATION WEIGHTS". The EMAIL_IP is the most
specific option, so it is the most likely choice in such case, but you could base the
reputation system on any of the remaining scores. Each of the enabled reputations adds a
new entry to the database for each new identificator. So while for example the number of
recorded and scored domains may be big, the number of stored IP addresses will be probably
higher, and would require more space in the storage.
3. Disabling the ""txrep_track_messages"" avoids storing a separate entry for every
scanned message, hence also reducing the disk space requirements, and the processing time.
4. Disabling the option ""txrep_autolearn"" will save the processing time at messages that
trigger the auto-learning process.
5. Disabling ""txrep_welcomelist_out"" will reduce the processing time at outbound
connections.
6. Keeping the option ""auto_welcomelist_distinguish_signed"" enabled may help slightly
reducing the size of the database, because at signed messages, the originating IP address
is ignored, hence no additional database entries are needed for each separate IP address
(resp. a masked block of IP addresses).
Since TxRep reuses the storage architecture of the former AWL plugin, for initializing the
SQL storage, the same instructions apply also to TxRep. Although the old AWL table can be
reused for TxRep, by default TxRep expects the SQL table to be named "txrep".
To install a new SQL table for TxRep, run the appropriate SQL file for your system under
the /sql directory.
If you get a syntax error at an older version of MySQL, use TYPE=MyISAM instead of
ENGINE=MyISAM at the end of the command. You can also use other types of ENGINE (depending
on what is available on your system). For example MEMORY engine stores the entire table in
the server memory, achieving performance similar to Redis. You would need to care about
the replication of the RAM table to disk through a cronjob, to avoid loss of data at
reboot. The InnoDB engine is used by default, offering high scalability (database size
and concurrence of accesses). In conjunction with a high value of innodb_buffer_pool or
with the memcached plugin (MySQL v5.6+) it can also offer performance comparable to Redis.