Two recipients are configured with the same e-mail address

I saw a post with a similar question, but did not understand the fix, so here goes.
Exchange server using POP3 connector to retrieve all mail from a domain.
Only using SMTP to relay outbound mail.
Whenever someone outside the company sends email, the email is delivered but the sender recieves:

The following recipient(s) could not be reached:

     Blow, Joe on 3/29/2006 7:46 AM
            A configuration error in the recipient's e-mail system prevented delivery of this message.  Two recipients are configured with the same e-mail address.  Contact your administrator.
           <swd.local #5.1.4>

How do I fix this.
This happens for ALL users in the domain.
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This error occurs when two objects have the same address as a proxy address, and mail is sent to that address.

greetrufusAuthor Commented:
All account are doing this.  Where do I find the duplicates?

I'm not sure I understand your comment.
are you sure your exchange server is creating this message?  (sounds fairly obvious that it does with you post indicatating :"<swd.local #5.1.4>")
stop SMTP outbound, test inbound from an external email source, and look at the queued outbound mail.

Also maybe try another POP connector, such as GFI mail essentials, free trial will suffice to try.  You are using SBS? (it has pop connectors, Exchange does not.)  Try posting in SBS TA
greetrufusAuthor Commented:
It appears to have been an ISP issue.
You can close this question!
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