I'm seeing conflicting opinions on the matter. If it is web mail, then it most likely is not using IMAP. so, should Mail AV be unchecked?
Basically, Gmail has its own A/V as you know; See the following links:
- Anti-virus scanning attachments - Gmail Help
Indeed, if you use the gmail web platform, the "Mail Antivirus" is useless but I would advise to let the "File Antivirus" option ticked to check in real-time the coming files like an attachment downloaded, just in case Gmail A/V hasn't seen it.
I hope it will clarify things up,
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