Several users are getting "452 <desination e-mail address> domain size limit exceeded" error message when sending to an external POP3 mail server which is the same as the originating mail server. I've Googled the error, searched for it in MS KB, and in this forum, all with no help. All ideas appreciated. Thanks, Mark P.S. Anybofy know of a good white paper that will lead me through bringing the external mail server in-house to the existing Exchange 2003 server? Need firewall port help, etc.

Did you check with your provider? Is it always the same users receiving this message? Do they send a lot of email? If not I'd check their machines for virus.

No, I haven't checked with the ISP, as it seems to be a local Exchange error message. 1) It comes back immediately and 2) If the user selects "work offline" from the Exchange server in Outlook 2007, they can send the message. The users and the recipients seem to be random, but all in the domain hosted offsite (.org as opposed to .local) Not a lot of e-mail and not big ones. POP mail is removed from the remote server. Viruses are checked daily by Symantec orporate 10 (which I hate!) Thanks for replying. Mark