I would like to add that I have this problem, and yet, I am receiving it even
though:
1. My emails do get sent
2. They are moved successfully from Outbox to Sent Items
3. My Outbox is empty when I receive this error.

The error is reported with an "Unknown Error" description in MS Outlook 2007.

Please could somebody from Microsoft help all of us?

"NDG" wrote:

How to fix error message "sending reported error (0x80040201)?