Our Mail Server (a Xen virtual server) was acting up yesterday. We could send email internally and also receive email from external source but if anyone outside of our company would send an email to any of us, No One could get that email?!

I Looked in all the log files and  all over the Net for the similar problem but any way the problem was not related to DNS or DHCP But the CLAM (The anti virus/virus-checking program). CLAMD was taking up too much memory.

The problem was due to lack of memory assigned to the Virtual machine changed the Config files on the Host Server (for the guest/mail server) and Reconfigured Clamd to be a little less dumb and every thing was working fine.

Just wanted to share since the log files did not indicate any thing clearly. It just said  ;

 "messages in queue: 76
 messages in queue but not yet preprocessed: 0 "

 so u get an idea that every thing was processed lol