I am quite curious about the circumstances of this question. I was not aware that Dovecot actually offered mail submission service. If Dovecot does offer such a service, then it will have to relay the submitted mail to the real MTA, which is very likely not Dovecot. At the moment I have Postfix set up as MTA for that purpose —

Relaying on port 25 is usually quick and easy to whitelist for certain permitted hosts, but otherwise port 587, optionally with STARTTLS, and/or port 465 with SSL/TLS is generally set up for user authenticated mail submissions.

See also:
https://www.mailgun.com/blog/which-smtp-port-understanding-ports-25-465-587/

On July 28, 2021 6:10:28 AM AKDT, Dan Conway <darkc0de@archnix6.net> wrote:

Hello,

Is it possible to disable the requirement for authentication on the 
submission service? I'm trying to require authentication for all, except 
for a handful of IP addresses.

Thank you.


ehlo test.com
250-aaa
250-AUTH PLAIN LOGIN
250-BURL imap
250-CHUNKING
250-DSN
250-ENHANCEDSTATUSCODES
250-SIZE
250 PIPELINING
MAIL FROM:<test@test.com>
530 5.7.0 Authentication required.

--
Sent from my Android device with K-9 Mail. Please excuse my brevity.