If you get a message similar to:
“Unable to move message to trash”
Tap Settings
Tap Mail, Contacts, Calendars
Tap your account name
Tap Advanced
Tap each folder (draft, trash, sent, etc) and select the appropriate folder for it. Do this even if it is already selected. (You will see a checkmark next to it after it is selected)
If you need need additional help, please email support@eve.net