How to add support to OpenSMTPD to distinguish between MTA and MSA operation mode?

Hi misc@,

I just started to read OpenSMTPD sources. Regarding the latest
discussions on tech@, there maybe seems to be the need to instruct
OpenSMTPD listeners to behave differently when acting as MTA or MSA.
Reading man smtpd.conf(5)[1] there is an option to add a tag to the
"listen on [socket]" directive. Those tags are currently used in "match"
directives. Maybe this could be extended to add well known tags to a
listener to control operation modes like MTA or MSA. Both of this is
documented in corresponding RFCs. Is there any interest for me to take a
closer look any maybe come up with some patches tech@? I am really just
starting to read OpenSMTPD sources. If there already is a way to
instruct OpenSMTPD listeners to behave differently regarding to - for
example - handling message ids based on in either MTA or MSA mode,
please let me know. I would like to avoid spending time into this, if
there is no interest but I think there really should be a way to
configure listeners to specific operation modes like MTA or MSA.

[1] <http://man.openbsd.org/smtpd.conf>

--
Christian