So another several wasted hours...
delete all content > restore from backup = same result (resurrected emails)
delete all content > restore as new = same result
delete all content > restore as new = same result
delete all content > iTunes restore as new = same result
delete all content > restore as new > delete all content > restore as new > delete all content > restore as new = same result
Each time more than 5 emails are deleted - the Trash folder resurrects any mails that have been handled on the device.
Additionally, 6 test messages sent from POP and IMAP accounts, none of the messages had any content just a header:
- the first message received sent from IMAP - displayed “not downloaded…”
- 2nd & 3rd messages received, correctly displayed - “message has no content”
- the 1st & 2nd message sent from POP, correctly displayed - “message has no content”
- 3rd message, displayed “not downloaded…”
I'd say that 9.2 still has some bugs.
Another day to look forward to with Apple Support - oh goody!