Integration with MailScanner

MailScanner and Exim with multiple queues

Abstract

Newer (since 4.92 I believe) Exim MTA are able to process messages on multiple queues. This gives us a new approach for MailScanner integration.

Message flow in a two-queue Exim setup with MailScanner

• Excactly one Exim daemon is running (exim -bd -q3m)

• Messages are accepted via SMTP on port 25

• Incoming messages are placed in the queue named "mailscanner" (and logged as Q=mailscanner in the common mainlog)

• MailScanner picks the messages and moves them to the default queue if done

  SMTP> :25 ---> [ Exim Listener (-bd) ]
                   |
                   v
                  Queue "mailscanner"   ($spool_dir/mailscanner/input)
                  via MAIL ACL
                   |
                   |
                   v
                 [ MailScanner ]
                   |
                   |
                   |
                   v
                  Queue "default"    ($spool_dir/input)
                   |
                   v
                 [ Exim Queuerunner (-q3m) ]
                   |
                   |
                   v

Exim setup

We use Exim’s "named queues" feature and start Exim in "combined" mode (one daemon as listener, forking queue runners from time to time).

Tools:

• Exim now understands a -qG<queue-name> command line option for queue operations

• Exipick now understands --queue <queue-name> command line option (since 4.93+fixes)

  ,---[ exim4.conf ]--------------------
  | CONFDIR = /etc/exim4
  |
  | # Use the MAIL ACL to place incoming messages into a non-default queue
  | acl_smtp_mail = acl_check_mail
  |
  | begin acl
  |
  | acl_check_mail:
  |
  |   …
  |
  |   # When accepting the message, we deliver it to the "mailscanner" queue (not "input"!)
  |   accept queue   = mailscanner
  |          control = queue_only
  :
  :

MailScanner setup

,---[ Mailscanner.conf ]----------------------------
| # Main configuration file for the MailScanner E-Mail Virus Scanner
| …
| Incoming Queue Dir = /var/spool/exim4/mailscanner/input
|
| # Set location of outgoing mail queue.
| # This can also be the filename of a ruleset.
| Outgoing Queue Dir = /var/spool/exim4/input