Several of our users have reported a problem where certain emails are not being sent properly.
The messages appear in the Sent Items folder, but the "From" field is blank. Message tracking on the server indicates that the messages are not going out. The problem is intermittent; sometimes a message to a recipient will fail just a few minutes after another message from the same user to the same recipient has succeeded.
I wonder whether this may have something to do with the way email addresses are saved for the contact? We can sometimes force the message by typing the actual email address (rather than the Outlook "Display As") in the "To" box, or by deleting the email address from the contact, saving the contact & then adding the email address back.
This is very frustrating as we now have to check our Sent Items folders regularly.