How to fix “Unable To Move Message to Trash” error on iPhone

This only happens if you are using IMAP server for your email, it’s not an issue on POP mailboxes.  This error appears on iOS devices such as iPhones and iPads when you try to delete or move email.  To fix this, follow the below procedure:-

1.    Tap Settings
   
2. Scroll down and click “Mail, Contacts, Calendars”
3. Select your email account and tap
4. On the “Account”, tap the email address, scroll down then tap “Advanced”
   
5. Under “INCOMING SETTINGS”, tap “IMAP Path Prefix”, at the end of the line, replace / and type INBOX (in capital letters)
   
6. At the top left, tap ‘Accounts’ then ‘Done’ twice to close the settings
7. On your device, press the Home button, then re-open Mail
8. You will now be able to delete or move your emails on your iPhone or iPad.