Tomasz Chmielewski wrote:
> With Postfix, it is possible to do "before-queue filtering"[1] (where
> mail is accepted only when filtering says it's OK).
>
> Can I make a similar setup with Exim? If yes, could you point me to Exim
> documentation describing such setup?
>
>
> [1] http://www.postfix.org/SMTPD_PROXY_README.html
>
>
Essentially ALL of it.
Exim's 'acl' case structures do the bulk of the work.
Exim's historical advantage is the ability to do all manner of
conditional testing DURING the smtp phases, beginning with 'connect'.
'system filters' also exist, as do router/transport conditionals, from
simple to very complex, but most of us do the bulk of the work in acl's
so as to intercept and shed bad-actors as early as possible, with use of
as meagre resource load as can be, and with greatly reduced (even NO)
need to generate post-smtp-session DSN's.
Exim impelements a whole different mindset from Postfix, so job one is
to NOT try to apply Postfix ways to Exim - it will just slow you down.
HTH,
Bill
