Thoughts on MSMilter

Shawn Iverson iversons at
Thu Nov 22 03:22:33 UTC 2018

sendmail compatibility interface is not an option, see

QMQP may be a good option.  I will check into this method....

On Wed, Nov 21, 2018 at 9:19 PM Mark Sapiro <mark at> wrote:

> First a big thank you to Shawn for all the work on MSMilter. I think at
> this point with the merge of
> <> it is working very well. It
> also provides a framework for adding even more checks at incoming SMTP
> time.
> There is one thing that I think could be improved in the current
> implementation. The milter is invoked by Postfix via the smtpd_milters
> configuration on all mail that arrives via SMTP. In most cases, it tells
> Postfix to DISCARD the message meaning the SMTP client is told the
> message is accepted but Postfix doesn't queue the message for further
> processing. The milter in turn has queued the message for MailScanner,
> and MailScanner processes the message and may queue messages back to be
> picked up by the milter and redelivered to Postfix.
> The issue is the milter reinjects the message via SMTP to postfix. This
> means the milter will be invoked again to process the message it just
> reinjected. For this reason, the milter just accepts all messages
> arriving from the local host so they can be processed by Postfix and
> avoid and endless loop through MailScanner.
> This all works, except it means that other messages arriving via SMTP
> from the local host are just accepted by the milter and not seen by
> MailScanner. This is not a major issue as such messages are usually only
> generated by trusted users or processes, but this could be avoided if
> the milter reinjected scanned messages using QMQP or the Postfix
> sendmail command.
> --
> Mark Sapiro <mark at>        The highway is for gamblers,
> San Francisco Bay Area, California    better use your sense - B. Dylan
> --
> MailScanner mailing list
> mailscanner at

Shawn Iverson, CETL
Director of Technology
Rush County Schools
765-932-3901 option 7
iversons at
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