> On Aug 27, 2019, at 10:10 PM, Eliza via Exim-users <exim-users@???> wrote:
>
> Is exim a multi-processes MTA,
No, Exim is largely monolithic, with the same process accepting
the inbound message and delivering it (modulo some messages being
queued for later delivery).
> While postfix is a threads powered MTA?
No, Postfix is not multi-threaded. Rather different stages
of message processing are handled by separate services:
http://www.postfix.org/OVERVIEW.html
So the key architectural difference is that Postfix is not
a single monolithic program, but a collection of programs
that handle various aspects of message processing. Monolithic
programs are more difficult to secure.
-- Postfix developer perspective below:
The most significant user-visible difference is that Postfix
has a queue-manager, which implements advanced concurrency/fairness
controls.
On the other hand, Postfix has fewer built-in content inspection
features, relying instead on external milters and (SMTP or just
unix pipe) content filters.
Postfix is optimized for security, performance and ease of
configuration at the cost of a more spartan set of built-in
content inspection features.
I'll leave to Exim developers to highlight key aspects of
the Exim architecture and user-visible features.
--
Viktor.
