I run postfix/dovecot/spamassasin/clamav/amavis mail server. Recently (maybe 1 month) I find about 500 undelivered e-mails in my mailq. I delete them, but I guess it is not a helathy permanent solution to my problem.
And then I have problems to deliver e-mails due to the sending MTA's poor reputation.
Example of log entry in mailq:
A19EC23DE0 4613 Tue Aug 1 06:57:01 MAILER-DAEMON
(delivery temporarily suspended: connect to hayatdiyaliz.com[185.140.110.3]:25: Connection refused)
jack3p0gz7b@hayatdiyaliz.com
There are about 20 "fake" domains like hayatdiyaliz.com and 20-50 e-mails per domain. The mailboxes' names are always like this "name"."multiple_random_characters"@domain.com
jack8d7413@domain.com
emily8186ga@domain.com
william564av4@domain.com
Do you have any idea how to prevent this situation and what steps should I take to do something about the MTA's poor reputation?
I added this to my postfixs main.cf, but that did not help:
smtpd_sender_restrictions = reject_unlisted_sender
Thank you
EDIT: the Fighting Spam - What can I do as an: Email Administrator, Domain Owner, or User? question is too wide-range, I thought maybe someone had this particular problem, It used to be okay, all test I tried online were OK, deliverability tests, open relay test, etc.