Blocking unwanted login attempts to SMTP

[Karel]

I have some rules set up in CSF to block unwanted login attempts to SMTP.
But apparently my setup blocks also the reception/delivery of mail from GB.

CC_DENY_PORTS = GB, plus a lot more of country codes
CC_DENY_PORTS_TCP = 25,465,587
CC_DENY_PORTS_UDP = 20,21,53

Perhaps my understanding of how a server works is incorrect.

I also enabled Enable login failure detection of pop3 connections and Enable login failure detection of imap connections

Please advice.

[ForumAdmin]

What you're attempting is not possible as SMTP authentication takes place over port 25 which is the port over which email is relayed.

[Karel]

Ok, thanks. Will have to trust the login failure detection then.
I suspected my setup was faulty, thanks for confirming.