We are currently using Symantec AntiVirus for SMTP gateways for PC. But
most of our servers are Linux servers now. I wonder if someone can
advise what Linux based smtp gateways software can replace this one?
Symantec AntiVirus for SMTP gateways basically does the following things:

Virus check of all the incoming emails
Spam block
White list
black list

Your comments will be greatly appreciated!!!

Thanks a lot!