Hello,
I was just looking around and noticed this. There's actually a good reason for why IMAP can't be supported. Every consumer antivirus software and all of its features are designed to protect a computer locally, meaning only the files itself that are within the computer are the ones that the security software can detect and manage. Now from my understanding, IMAP is a protocol wherein your email are only viewed from an email server (in a remote location) through your computer. Therefore, the antispam can't move the emails directly since the emails aren't really in your computer in the first place. For the antispam to do this, it is required that the program be installed in the email server itself. Now for POP I think the emails itself are downloaded to your computer's hard drvie from the email server so in that way, the antispam can move the messages around. I hope this helps!