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Pipe incoming email for certain user to external script

This tutorial explains how to pipe incoming email for certain user to an external script (it must be a file on your mail server, not a remote file accessible via ssh/http/ftp/...).

Configure Postfix to use your external script as transport

To pipe incoming emails to external script, you must add your external script as Postfix transport program. Please add below line at the bottom of Postfix config file /etc/postfix/master.cf:

external-pipe   unix    -   n   n   -   -   pipe
    flags=DRhu user=vmail:vmail argv=/path/to/your/external/script.sh

Note:

• You can use some macros to replace with corresponding information from the Postfix queue manager delivery request. Refer to Postfix manual page pipe(8) for more details. For example:

external-pipe   unix    -   n   n   -   -   pipe
    flags=DRhu user=vmail:vmail argv=/path/to/your/external/script.sh -f ${sender} -d ${user}@${domain} -m ${extension}

• the second line needs to be right under the first line and must start with one (or more) whitespace, and the first line cannot start with whitespace, otherwise postfix will fail with unexpected command-line argument errors. Also make sure the user= line is pointing to a valid user with permissions to execute the script. This user must not be the postfix or root user, otherwise or the pipe will fail.

Now restart Postfix service to make this new transport available:

# /etc/init.d/postfix restart

Update per-user transport to use this new transport

We need to update per-user transport setting, so that all emails delivered to this user will be piped to this new transport - your script.

• If you have iRedAdmin-Pro:

  • For iRedAdmin-Pro OpenLDAP edition, please go to user profile page, under tab Advanced, set Relay/Transport setting to external-pipe. Screenshot:

* For iRedAdmin-Pro MySQL or PostgreSQL edition, please go to user profile
  page, under tab `Relay`, set `Relay/Transport setting` to `external-pipe`.

• If you don't have iRedAdmin-Pro, please update LDAP/MySQL/PgSQL database to use this new transport.

  • For OpenLDAP backend, please login to phpLDAPadmin, add new attribute mtaTransport for your user, set its value to external-pipe.

  • For MySQL/PostgreSQL backend, please execute below command with SQL command line tool (Replace 'user@domain.ltd' by the real email address):

sql> USE vmail;
sql> UPDATE mailbox SET transport='external-pipe' WHERE username='user@domain.ltd';

That's all.