Provided by: courier-mta_1.0.16-3build3_amd64 bug


       dot-forward, dotforward - Read $HOME/.forward


       $ cat $HOME/.courier
       || dotforward


       The dotforward program is a compatibility module that reads forwarding instructions in
       $HOME/.forward.  dotforward is used for compatibility with sendmail or other mail servers
       that use the $HOME/.forward file. The dotforward program is intended to be executed from a
       dot-courier(5)[1] delivery instruction file. The system administrator can add it to the
       default set of delivery instructions, thus unilaterally implementing $HOME/.forward
       systemwide. To read forwarding instructions from $HOME/.forward, put "|| dotforward" on
       the first line of $HOME/.courier*. "|| dotforward" can also be added to the
       DEFAULTDELIVERY setting in the courierd configuration file. In both cases it must be
       followed by a newline, and the remaining delivery instructions, which will be used if
       $HOME/.forward does not exist.

       dotforward expects to be invoked from dot-courier(5)[1] delivery instruction file via the
       "||" operator (or from DEFAULTDELIVERY).  dotforward checks its environment, reads the
       message from standard input, reconciles its environment with the contents of
       $HOME/.forward, then prints on standard output equivalent dot-courier(5)[1] compatible
       delivery instructions. The "||" operator reinterprets dotforward's output as additional
       delivery instructions, by the Courier mail server.

       The different security models of the Courier mail server and other mail servers that use
       $HOME/.forward, such as sendmail, means that it is not possible to faithfully duplicate
       100% of the behavior of $HOME/.forward that originated with sendmail. The following
       section documents the behavior of the dotforward utility in the the Courier mail server
       mail server.

   $HOME/.forward processing
       dotforward reads the DTLINE environment variable, and the headers of the message being
       delivered, from standard input.  DTLINE contains the recipient's E-mail address. The
       Delivered-To headers list the recipients that already received this message. This is used
       to prevent mail loops between $HOME/.forward files from different recipients, which
       forward mail to each other.

       If $HOME/.forward does not exist, dotforward quietly terminates with a zero exit code,
       doing nothing. The remaining delivery instructions in $HOME/.courier are then carried out.

       If $HOME/.forward exists, it is expected to contain a list of addresses that the message
       should be forwarded to. An address may be an actual E-mail address, or a name of a program
       or a mailbox. Each line in $HOME/.forward should contain a list of comma-separated
       addresses. Use "| /path/to/program" (including the double quotes) to specify a delivery to
       a program (the message is piped to the given program). Use "/path/to/mailbox" or
       "./path/to/mailbox" (again including the double quotes) to specify a delivery to a mailbox
       (relative to $HOME in the second case).

       "| /path/to/program", "/path/to/mailbox", and "./path/to/mailbox" may also be listed on a
       line by themselves without the double quotes.

       All other addresses are interpreted as E-mail addresses where the mail should be
       forwarded. Any backslash at the beginning of an E-mail address is removed. Backslashes are
       used by sendmail to prevent mail loops. The Courier mail server does not need the
       backslashes -- it uses a different mechanism to prevent mail loops.

       Every E-mail address is checked against the list of E-mail addresses found in Delivered-To
       headers. If the E-mail address specified in $HOME/.forward matches any address in the
       Delivered-To header, it is automatically removed from a list of addresses.

       dotforward normally terminates with the exit code set to 99. This results in the Courier
       mail server considering the message to be succesfully delivered, and any additional
       delivery instructions in the .courier file will not be carried out. If an address read
       from $HOME/.forward matches the address in the DTLINE environment variable, the address is
       removed from the list of addresses that the message will be forwarded to, and dotforward
       terminates with the exit code set to 0 (after printing all the relevant delivery
       instructions to standard output). The messages will be forwarded, and the Courier mail
       server will proceed with additional delivery instructions in the .courier after finishing
       with the delivery instructions it reads from dotforward.


       The restrictions and precautions mentioned in dot-courier(5)[1] are also applicable here.
       There is an upper limit on the maximum number of characters that are read from any process
       executed by ||. Also if any delivery instruction fails with a transit exit code, the
       message will be completely redelivered at a later point, even to all the addresses it has
       been succesfully delivered the first time around.




       Sam Varshavchik


        1. dot-courier(5)