We have recently become aware that in some cases, after Outlook updates, new emails that are sent are not being stored in the Sent Items folder.
This should be considered a critical problem by most people but as most of us don’t look in Sent Items very often, we may be assuming that emails are there when they are not. The most serious aspect of this is that those missing emails are not recoverable. This is not to be confused with emails missing from the Inbox which may relate to a different problem
Fortunately, it’s an easy fix and here is how to do it.

In Outlook, Click on File, Options.
In the Outlook Options window, click onto Mail, scroll down to the Save Messages section.
Make sure the check box ‘Save Copies of messages in the Sent Items folder’ is checked.