Undeliverable : I can receive, respond, but not send to a contact

[Kelly O]

I have a couple of contacts that I have just begun to have trouble with. I
can receive their e-mails, respond to their e-mails, but can't initiate an
e-mail. Any help? This is the message I receive:
Subject: test #2

Sent: 4/22/2008 3:34 PM



The following recipient(s) could not be reached:



Urish, Jim on 4/22/2008 3:34 PM

The requested operation failed.

 

[Russ Valentine [MVP-Outlook]]

Help would require your providing some actual information when you post.
"can't initiate an email" means what exactly? The possibilities are endless.
Be precise.
Do not fail to include other relevant details such as Outlook version,
information store, transports, etc.