We are currently using GFI Mail Essentials as an SMTP server alone with Checkpoint firewall anti-spam.
GFI checks for, spam, viruses and attachment. They do a decent job in general but still use old 15+ year logic.
we do host a couple of exchange servers with 200+ users. What would be a good Anti Spam with antivirus and attachment checking email filter possibly with email encryption to replace GFI ME. Google use resale Postini to non google apps users before. Very important this question is posted for a real expert with 10+ years of experience.