[Rspamd-Users] Q: adjusting Subject header

[G.W. Haywood]

Hi there,

On Sun, 2 Jul 2023, Piotr Klaban wrote:

> .. by looking at the milter connection between rspamd and postfix,
> no subject is part of communication.  I would not dig deeper, till I
> will understand how to correcly use rspamd in milter communication.

The milter must ask the MTA for whatever it needs to see.  Usually a
part of the milter configuration arranges for that to happen.

The specification for the milter interface permits a milter to give to
the MTA (Postfix in your case) an instruction to rewrite a header, but
this can take place only at the "End Of Message" callback[*].  Usually
by that point the milter has already seen everything in the message
which it needs to see - including the headers - but it isn't actually
necessary for the milter to see anything in the message.  It can if it
wishes (within the limitations of the SMTP specifications) rewrite any
header with any text.

When I first met the milter interface I found it rather unintuitive.
My opinion about that hasn't changed, but at least I can now see the
reasons behind it.  Basically it's following the SMTP conversation,
and given that SMTP is effectively set in stone there's very little
room for manoeuvre.

[*] See for example

.../libmilter/docs/design.html
.../libmilter/docs/overview.html

in the Sendmail sources which you can find for example at

https://ftp.sendmail.org/sendmail.8.17.2.tar.gz

I'm sorry but I'm not familiar enough with the Postfix documentation
to know if there are passages in it to which I could point you.

-- 

73,
Ged.