We have Antivirus based on ClamAV in Visual Basic 6.
Now we need Anti-Spam for this and required all features for Anti-Spam like in [login to view URL]
We need Engine must be ClamAV because it is Royalty FREE and under GPL.
I have experience to install and configure antispam gateway based on open source software (clamav / spamassasin / postgrey )
It, better to install the gateway on linux os.
Regards
If recomended on linux server, but you will be on any server (Win/Linux/Mac) mail carpets, and use a gateway mail proxy, or a separated Antispam mail verified server. Of course, Clamav and Spamassasin.
How many users emails?