Outlook - Undeliverable email

[Darryl]

I have a few people who are unable to send email to my domain (NWE.CA)
from Outlook. It is only a handful of people. Many Outlook users can
send to the domain without any problems. The people who cannot send
are in various different companies with various ISP's (nothing in
common really except Outlook).

They recieve an email from 'System Administrator' instantly saying
that the email was undeliverable. The reason for the message being
undeliverable ranges from nothing at all to 550 5.1.1 unknown or
illegal alias:, etc...

Anyone have any idea why this might be happening? There is nothing
wrong with the MX record for NWE.CA (as far as I can tell). One of
the PC's that cannot send from Outlook to NWE.CA has no problem
connecting to NWE.CA's mail server using Telnet. Outlook can even
send to a different domain on the same mail server as NWE.CA without
any problem.

Your help is appreciated.

 

[Jeff Stephenson [MSFT]]

http://office.microsoft.com/assistance/preview.aspx?AssetID=HA011128331033
explains this error and what to do about it.

 

[Darryl]

Thanks for the reply. I found out about 2 hours after I posted this
message that our ISP had put our domain on their DNS servers and mail
servers even thought they were not our hosting company. Therefore
anyone using their email server (they are a large ISP) was having
email rejected to our domain because the ISP's mail server had no
email addresses listed for our domain.

Anyhow, not an Outlook problem. Thanks.