How do I avoid "message could not be moved to the mailbox Trash" on iOS 10?

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?


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.


The issue is caused by the way iOS names the IMAP prefix in IMAP based mailboxes. It defaults to a prefix of / but it should be INBOX. If you change the prefix it will fix the issue.

To change the prefix:

  1. On your iOS device got to Settings
  2. Passwords & Accounts
  3. Click the mailbox name
  4. Click the email address where it says Account at the top
  5. Click Advanced at the bottom
  6. Tap where it says IMAP Path Prefix
  7. Type in INBOX instead of /
  8. Done!

Instructions on how to fix IMAP 'unable to send message to trash' error