I'm totally fine with build-in security in Windows since Windows 7. No need for even more resource hungry and privacy concerning software. I'm using only a few Windows systems to be honest but also never had a real security issue.
im also looking for new AV software for my home systems. I need 10 license count plus one win server. I currently have Avast business but lately i havent been impressed with them. IDK what they are doing but support has sucked and they are removing features, etc.
I don't use antivirus on my servers. The reason is quite simple, they have too many security and performance issues. Windows server is secure enough.
Note that none of my windows servers are exposed on the internet. They are all firewalled.
When using secure methods to ensure the reliable operation of your business, I use two-factor authentication of users with the generation of one-time passwords through universal security tokens. later, roundcube email provides additional reliability and makes this approach very convenient for users of any level.