Random Exchange delivery failures to internal people

[The2ndOmen]

Exchange is randomly generating delivery failures to local users. People also seem to be getting disconnected randomly using cached mode. I am running Exchange 2003 and Outlook 2003. This is affecting a small amount of users about 5 but it seems to be happening every day. The users mailbox that are reporting these errors do exist and work for some people but don't work for others.

The following recipient(s) could not be reached:

First name last name on 6/13/2005 9:28 AM

The e-mail account does not exist at the organization this message was sent to. Check the e-mail address, or contact the recipient directly to find out the correct address.

<exchange server.HeadwayCorp.net #5.1.1 smtp;550 5.1.1 User unknown>

 

[adcfaq]

disable the cache mode and moniting for a couple of days.

-----
Directory Services/Exchange Consultant

 

[The2ndOmen]

Now it seems these accounts are receiving internal but not receiving external email.

 

[The2ndOmen]

When I do tracking on the email in exchange I see a message SMTP: Non-Delivered Report (NDR) Generated. Any one know of any logs I can check to give me a better answer. These users are getting mail from some external users. I do not have any connection filters setup.