NAME

       maildirquota - voluntary Maildir quotas

SYNOPSIS

       maildirmake {-q} {10000000S} {./Maildir}

DESCRIPTION

       maildrop has a manual quota enforcement implementation that does use the quota facilities of the host
       operating system (filesystem-based quotas). This is an option that is set at configuration time, and may
       be disabled.

       Using filesystem quotas sometimes leads to problems. After a hard quota is hit, most commands issued by
       mail clients fail, including some commands that poorly-written mail software may not expect to fail, and
       therefore be unable to gracefully handle the unexpected failure.

       With manual quotas, the only operations that fail are the ones that most mail clients expect to fail,
       when the mailbox is full. However, filesystem-based quotas cannot be used in some situations, such as
       virtual mailboxes. If this experimental feature is enabled, approximate quota enforcement can be
       implemented by maildrop or deliverquota to whatever extent it's possible to do so. Quotas are enabled by
       the -q option to maildirmake. Both maildrop and deliverquota will observe any maildirmake-requested
       quota.

   LIMITATIONS
       This quota mechanism will only work as long as maildrop (or deliverquota) are the only applications that
       deliver messages to the maildir, or as long as other applications implement the same quota enforcement
       mechanism. The quota enforcement mechanism is described separately in the README.maildirquota.html file
       in the source code distribution.

       Quota enforcement will still work, to some extent, if there are other applications that deliver or modify
       messages in the maildir. However, quota enforcement may not kick in immediately when the maildir goes
       over quota, in fact the maildir can go over quota by a noticeable amount. But eventually, as long as
       maildrop or deliverquota are responsible for delivering the majority of messages, quota enforcement will
       kick in. Also, other sources of messages may also result in noticeable performance degradation, because
       quote recalculation will become noticeably more expensive.

       Also keep in mind that this quota mechanism is generally useless if mail recipients have direct access to
       their maildirs.

       Finally even under the best conditions this quota enforcement does have a small chance of a race
       condition where a maildir will go over quota by some amount. maildirs are designed for speed, and this
       quota implementation was designed to have as little additional overhead as possible, compared to regular
       maildirs. To enforce an exact quota you would have to use some kind of a locking facility, which will
       impose a drastic performance degradation on the overall maildir performance. A decision has been made to
       avoid locking, with the only negative side effect being a possibility of going over quota in very low
       probability situations.

       A way to minimize the risk of going over quota is to set reasonable quotas, in relation to maximum
       message sizes supported by your mail server. If you set your maildir quota to five gigabytes, for
       example, it makes very little sense to configure your mail server to accept messages up to three
       gigabytes in size. Your maildir quota should be chosen so that it makes sense when compared to the
       maximum message size allowed by your mail server.

   FOLDERS
       This quota implementation is compatible with a popular extension to maildir which defines individual mail
       folders within a single maildir. However, in order to create a compatible folder, you MUST use the
       maildirmake command that comes with maildrop, and you MUST use the -f option to maildirmake, giving the
       name of the folder. Do not use maildirmake and specify the directory name of the maildir folder. Quota
       enforcement will not work if you do that.

SEE ALSO

       maildrop(1)[1], maildirmake(1)[2], maildropfilter(5)[3], deliverquota(8)[4].

AUTHOR

       Sam Varshavchik
           Author

NOTES

        1. maildrop(1)
           [set $man.base.url.for.relative.links]/maildrop.html

        2. maildirmake(1)
           [set $man.base.url.for.relative.links]/maildirmake.html

        3. maildropfilter(5)
           [set $man.base.url.for.relative.links]/maildropfilter.html

        4. deliverquota(8)
           [set $man.base.url.for.relative.links]/deliverquota.html

Courier Mail Server                                08/25/2013                                    MAILDIRQUOTA(7)