I have one Exchange 2003 user that has NDR messages from only one source (an external e-mail account). I receive NDR reports that have this error message "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.The MTS-ID of the original message is:groupwise.407ECA3E.D7C:d:c26d:N". Yet the e-mail address, in the NDR is correct. I suspect that it has something to do with a Groupwise server (due to the the content of the error message). I "tweaked" some of my X400 connections, but seem to be still getting the error messages, from that particular source (other Groupwise servers are able to send e-mail to us). Below is another NDR error message. "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.The MTS-ID of the original message is:groupwise.407EC978.987:d:c26d:N".