"Sent" emails disappearing into the void:

There is another discussion on this going on, yet since it has been wrongly labeled as "answered", I guess the Apple staff haven't been following it. So I'll start a new one.

Here is the situation: Starting from iOS 7 regardless of device, many users have been experiencing the issue where, you write or respond to an email, hit send, and the message appears to have been sent. Yet the message is not sent, and doesn't appear in Sent or Drafts folders (nor "Outbox" folder in case of Exchange email systems). The intended receipients never receive the message, and no copy of it seems to exist anywhere.

Apple has suggested users simply delete the account from the phone, then re-create it. That seems to solve the issue, but only temporarily. Within a few days, the problem is back. Upgrading to the latest version of iOS doesn’t help either.

This is really crippling for an office where my users rely on their iPhones and iPads quite heavily when communicating with clients.

PLEASE HELP!!