Square symbol next to sent folder in apple mail

jtmls wrote:

I recently updated a mail account and when I sent a text email it went to the On My Mac folder rather than the normal sent folder and a weird square symbol appeared next to the sent folder. The sent folder now contains obvious gibberish files. I have seen references to this phenomenon in other posts but no clear solution. I have deleted the account and reinstalled it without effect.

Verify your Mail>Preferences>Accounts>Mailbox behavior

Mail User Guide - Apple Support

jtmls wrote:

Thanks very much. This was exactly what I needed!

Good computing jtmls !