Can't delete email
I often have to delete any given email 1-3 times, and sometimes it won't delete at all, in spite of my settings which tell it to do so. I use the iMail app in conjunction with Gmail.
Mac mini 2018 or later
Question marked as
In Mail>Preferences for that account> Mailbox behaviors, make certain move to Trash isn't pointing to an On My Mac mailbox, but to the Trash box on gMail's server.