You may see the error message below when moving or deleting an email on your iPad or iPhone.
Unable to Move Message: The message could not be moved to the mailbox Trash.
When this happens, you might perform an action like deleting the message, and while it will disappear temporarily, Mail will then show you a notice that states the message could not be moved, and it will then reappear in your mailbox. If you have multiple accounts configured in Mail, then this may happen for only one or two of them, so the error will only happen on messages in those accounts, as opposed to all the time.
What causes this is that the IMAP Path Prefix hasn’t been set up properly. This can happen with IMAP accounts that require that the Path Prefix be set to INBOX. Check the simple steps below to fix this issue.
Please click on the short video below that highlights some of the steps to fix this issue.
Please test after each step:
1.Go to Settings > Mail, Contacts, Calendars > Your Account > Mail > Turn Mail off and then, wait a few seconds, on.
2.You may try deleting the email account from your iPhone or iPad. Just tap Settings > Mail, Contacts, Calendars > Your Account > and tap Delete Account. Then re-add your account by going to Settings > Mail, Contacts, Calendars > Add Account.
3.Tap Settings > Mail, Contacts, Calendar > Your Account > Account > Advanced > Deleted Mailbox and set this to trash then tap Advanced > Account > Done.
4.Tap Settings > Mail, Contacts, Calendar > Your Account > Account > Advanced > IMAP Path Prefix, then enter Inbox; when you done, tap Account > Done.
6.Open your Mail app on your iOS device, then tap Index > Edit > find the email messages that you can’t move/delete and then select them > tap Mark and Mark as Read (or Unread).