When I logged on to my GMail web interface (the way I normally work with it), I found a new label named
[Google Mail]/Trash. It had a dozen or so messages that I recently deleted via Mail on my iPhone.
I confirmed that deleting messages from the phone was moving them to this new label instead of to the normal Trash folder.
I’m not sure specifically what the cause was, but I did all of the following which seems to have fixed it:
- Powered-off and rebooted the phone
- Went into mail settings, and for each of the major categories of folders (Drafts, Deleted, Archive), I reset each one to the “On My Phone” local folder, and then set them all back to the correct server-side folders:
And then it all seemed to work properly again.
I don’t know what the cause might be, but I’m guessing that Google changed their internal label-name that they use for Trash, so when iOS used the old name, it showed up as a new label. Then changing the folder elsewhere and back reset it to the new name provided by the server.
At least that’s my working theory until I learn otherwise.