Cannot send email to specific email server

[John Marthe]

We can receive emails from, but cannot send emails to
another company. Both them and us use 3rd party email
services. Each company has been granted domain name type
email addresses. Such as "(e-mail address removed)" where
futurecompnay would be the name of our business.
We are using outlook 2002 as our client. We have no
problems emailing anyone else.
The email stays in the outbox, waiting to be sent and we
get the error message:
Task '"outgoing email server" - Sending' reported error
(0x800CCC69):
'Unknown Error 0x800CCC69'

I substituted the name of our 3rd party email server
with "outgoing email server".

The problem only resides between our email addresses and
their email addresses. They can receive emails from others
and we can send to others with no problems.

Both 3rd party email service companies claim that they do
not have any blocks set on their firewalls or email
servers and that neither as using black lists.

The communication between our company and the other
company is vital and we need the email to work.
Please help.
Thanks, John

 

[Jeff Stephenson [MSFT]]

The error you're getting means that the server you're trying to send to is
saying that the destination mailbox was not found. It may be that the
local-part of the address (the part before the '@') is incorrect - verify
those. Is there any other text in the error message? Outlook should be
reporting the server's reply, which may contain more information.