Problem:
Outlook generates error code 0X80040201 when sending mail and mail sending fails as a result.
Reason:
This error usually occurs when a computer that was previously part of a Microsoft Exchange environment tries to send email to an address that was part of the same Exchange server but no longer is. As a result, Outlook tries to send an email to the alias or nickname associated with the recipient instead of the valid email address for that particular recipient.
Solution:
Update all entries in your address book that were formerly part of your Exchange setup. Ensure that all related entries have a full, valid email address.