I don’t know what exactly you mean with “completely deleted”. I think mails and attachment are deleted but probably not “completely wiped”. From what I see, when I delete mails with attachment and empty trash as well, the Mail app storage is reduced accordingly. Then I do consider they are deleted.
Ahh, OK so clearing storage is like ‘resetting’ ‘Mail’, it will delete all downloaded (emails, you refer to ‘email lists’) data on the phone, and settings - you have made/added.on the phone.
I dont ‘store’ emails on the phone, and delete those after reading, so guess the ‘clear cache’ would remove anything I couldn’t immediately see.
Can you selectively choose under ‘clear storage’ what you delete, ie email lists or settings.
Guess ‘clear storage’ if you could just select ‘emails’ would not hurt to do, but whilst hopefully retaining the accounts you would have setup.
Unfortunately not, “Delete Storage” will clear the whole app storage (it’s a standard Android feature).
Android is not aware of the app’s data structures, it will simply delete everything in the filesystem folders.