Exim accepting mail it should not - invalid account gets accepted

[Oriso]

Hello all,

We've run in a problem with Exim lately (in fact I can't say exactly when this started but we've seen the effects lately).

-Edit: Forgot to add that all email account are configured with :fail: to discard email at smtp time, but it doesn't seem to be working all the time

Exim seems to be accepting emails to pop3 account that do not exist, and I've been able to verify that behavious on 2 different servers we have. If I do a manual telnet connection, with ehlo, valid mail from: and rcpt to: being a bogus email address from a hosted domain, I sometimes get 550 error code, but it seems sometimes the email gets 250 Accepted. This is working hell on our spam server which creates a quarantine account for every account, and it verifies the account by doing the procedure stated above.

We filter email for more than just cpanel, so I cannot put cpanel directly on the net, it has to be filtered thorugh an external spam device, so the domains hosted on CPanel all have mx records pointing to that box instead. Email gets delivered correctly, so I do not think the configuration is that messed up, but I am wondering if the fact that the CPanel server is not the MX for the zone is causing it to accept emails when it shouldn't.

I cleared my mail queue Friday, to find 2200 mail messages, most for non-existing email addresses waiting to be bounced. This has caused us to get a poor reputation on senderbase.org since we "act" as a spam relay by bouncing emails.

If anyone had a clue why this is happening or could help me figure it out, I'd be grateful!

-Alain Gagnon