We previously noted an issue in which mail sent from the iPhone simply disappears into the void, never reaching its recipient, nor appearing in the "Sent Items" folder, and also never generating an error message indicating that anything has gone wrong.
In many cases, the fix for these issues is the same as one we noted for other mail-related problems: delete and re-establish the afflicted account. Tap Settings and then tap Mail. Tap on the problematic account, then scroll to the bottom and select Delete Account. Go back to the main Mail settings pane and tap Add Account … Read more