Unable to send e-mail to only one user on a domain

[shakatak]

Hello,

I have a user at our company that is unable to receive e-mail from users outside our company network.

Summary:
User1 from Domain A is can't send to User2 on Domain 2 but is able to send e-mail to user3, user4, and user5 on Domain 2.

This is the message the user receives when they try to send an e-mail to User 2 on Domain 2:

"The message could not be delivered because the recipient's destination email system is unknown or invalid. Please check the address and try again, or contact your system administrator to verify connectivity to the email system of the recipient."

Any ideas on what this might be????

 

[PU36]

If you are running Outlook 2003 and are in cache mode, remove the cache mode and then reconnect. Allow Outlook to refesh the Address Book and try again.

It is most likely a client side issue.