[Rspamd-Users] postsrsd and (DKIM signing) rspamd postfix milters together?

[Franta Hanzlík]

Hi,
I use Postfix + RSPAMD on our high school mail server (around 300 users, 
one domain, low traffic). RSPAMD works in self-scan mode (Unix socket 
communication) and also provides DKIM signing of outgoing mails.

Since many users have their mail forwarded to their external mail accounts, 
I would like to include Postsrsd (https://github.com/roehling/postsrsd) 
as a second milter.

Is this arrangement possible? If so, I assume that the PostSRSd milter 
should be included (listed in main.cf) after RSPAMD (so that it changes 
the sender envelope address only for mails that pass RSPAMD - and the 
fact that the envelope address and the "Return-Path" header changes 
should not be a problem for the email signature, since these items are 
not part of the signed data). Is this reasoning correct?

I have a vague awareness that the milter protocol allows the MTA (Postfix) 
to call milter several times during the mail reception (7-9? times, 
depending on the protocol version - in the Connect/HELO/MAIL FROM/RCPT 
TO/DATA/... phases) - I don't know if this can affect the processing 
in this case?
I guess it depends which phases the milters registers or in which 
phases they make decisions - but IMO this information is not very well 
known to most milters...

PostSRSd can also rewrite the mail sender envelope using Postfix 
"canonical maps" - but I somehow got the impression that using the 
milter mechanism should be somehow more advantageous... I don't know...
Can someone knowledgeable help?
-- 
Thanks in advance, Franta Hanzlik