Unknown Error 0×80040600
I got the Microsoft Exchange Server reported error (0×80040600) : ‘Unknown Error 0×80040600′. again today. Sure enough, deleting the messages in deleted items cleared the problem. When I then did a F9 synch 18 messages suddenly appeared in deleted items. Cleared those too.

11. January 2004 at 8:00 pm :
I receive error..
The message could not be sent because it rejected you as the sender. Server Response:’501 need user@domain at <John Pedersen@Fax Server’. (Account:’mail.comcast.net’,SMTP Server:’smtp.comcast.net’,Error Number: 0x800ccc78)
11. January 2004 at 9:46 pm :
Thats actually a completely different error message and is likely to be because your email address is not what the mail server at comcast is expecting!