My mum received a piece of spam, that could not be deleted or moved on her iPad using the mail app. It was only removed after deleting the account within the mail app, and recreating it.
Is it possible to send an email that can't be deleted from the mail app?
My mum received a spam email claiming to offer $500 at Sainsbury's (yes, $$ at a UK supermarket!). After opening the email on her ipad (with image loading turned on) she recognised this as an obvious scam and touched the "trash" icon to delete.
The email appeared to be deleted, (the animation showing the email moving to trash ran and the email went from her inbox). However the email was not moved to trash, and after restarting mail, the scam email was still in her inbox. She subsequently received several more spam emails (offering viagra etc), and all further attempts to delete the original email produced a dialog "Unable to delete this email [OK]". (the later spam emails could be deleted as normal, she had not previously had a problem with spam on this email address)
The email was sent through her ISP's IMAP server (talktalk). When she logged into the same email account on a windows PC the original spam email was not on the server.
She then asked me to help her sort this problem. I turned off image loading. Then I tried to move the spam email to "Junk", again it appeared to move but after restarting the mail app, it was back.
Next, I followed the instructions given at https://forgetcomputers.zendesk.com/hc/en-us/articles/201010530-Can-t-Delete-Email-from-iPad-or-iPhone- (to check the "On the server" next to the folders in the account view of mail settings). This did not solve the problem. The line "on the server" was already checked and I changed no setting. The email could not be deleted or moved to junk
Following another forum thread, I also tried setting the email as "unread". This had no effect, except marking the spam email as unread.
I then deleted her account in settings>mail, and created a new account (with the same email address) When she connected to the new account, the spam email was gone. So I hope the prime issue is now resolved.