Help Needed: My RHEL5 box suddenly stopped accepting e-mails

[Allen Chen]

I've read those posts, actually I have no idea about your environment.
so I can not help anything right now. can you post:
1. server OS version, is it a shared server or a dedicate mail server?
2. sendmail version: compiled or rpm?
3. Are incoming and outgoing mail services on the same machine?
3. do you use any spam filter or virus scan system? if yes, how?
4. do you use cyrus-imap? version? compiled or rpm? is it on the same 
machine?
5. Your internal network number? internal server IP?

Allen