User Unknown?

For some strange reason, I cannot send a message to my regular email using zoho mail.
I can however send it to an alias at the same mail host (google) with no problems
I can also send mail to this address form MSN, or any other mail program with no problems.

Here is a copy of the returned message in zmail:

This message was created automatically by mail delivery software.
A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. User Unknown :

[marc@creepycrawlythings.com]

Received:from 172.31.252.127 (172.31.252.127 [172.31.252.127]) by svwall.zoho.com
    with SMTP id 12326501762401000.8051967827913; Thu, 22 Jan 2009 10:49:36 -0800 (PST)
Message-ID:<11effad05fa.1418886408392551641.-5523529570416043248@mycoloradoschoice.com>
Date:Thu, 22 Jan 2009 11:49:29 -0700
From:"marc.dykstra" <marc.dykstra@mycoloradoschoice.com>
User-Agent:Zoho Mail
To:marc@creepycrawlythings.com
Subject:testing this
Content-Type:multipart/alternative;
    boundary="----=_Part_268_1486735384.1232650169711"from 172.31.252.127 (172.31.252.127 [172.31.252.127]) by svwall.zoho.com
    with SMTP id 12326501762401000.8051967827913; Thu, 22 Jan 2009 10:49:36 -0800 (PST)