Is there a community just for Mail?

I too prefer using the forum section for the macOS version your have, because your Mail version is linked to and updated with the OS versions.

macOS - Apple Community.

That way, responders don't have to burn a post asking which Mail version you have, and that can mean faster help.

barneyhairball wrote:

I need to ask a question about mailboxes, is there a community just for Mail issues?

No. Other Apple Apps & Services, or (probably better) macOS Sonoma.