Since upgrading to iOS 10, in certain e-mail accounts (notably an msn.com account) I cannot delete certain messages in Apple Mail. If I swipe left or open the message, and click the Trash icon, I get an error message
Unable to Move Message
The message could not be moved to the mailbox Trash.
This appears to happen only for messages that have already been deleted via a different client (e.g., Apple Mail on macOS) but that still appear in iOS. No matter how long I wait, these messages do not correctly sync with the iOS client on their own, and manually deleting them produces the error above.
All the instructions I've found online for addressing this (apparently common) issue either do not apply to iOS 10 or simply have no effect (repeating the same error). The only way to delete a message once this error occurs for it is to disable and then re-enable the offending account, or delete and re-add the account entirely. The account then correct syncs with the server and shows the already deleted messages as gone. But that only works until the error happens again.
How do I avoid "message could not be moved to the mailbox Trash" on iOS 10?
Best Answer
Here's what I did to fix things...
(EDITED, BECAUSE PREVIOUS WAY DIDN'T WORK... EVERYTHING REAPPEARED)
Go in to settings > Mail > Accounts > (Account Name) > shut off "mail"
Force quit the mail app; force quit settings app.
Re-open mail app. It should not show any mail from that account. Force quit mail app again.
Then reopen settings, re-enable mail. Everything is re-synced. Re-open mail app.