User not listed in Domino Directory

Some of our users are not receiving mails from outside our domino domain .They are sending emails successfully but when someone outside our domain tries to email them it bounces back with error " user not listed in domino directory". there is nothing wrong in their person document. Also their ID is fine .Other users are fine with both sending and receiving within and outside our domino domain. Can someone tell the solution.

Regards

Subject: User not listed in Domino Directory

Check that the owner of the mail file is correct. If the owner is not in the Domino Directory then replies will get this error message.

Subject: User not listed in Domino Directory

Hello there

Firstly I would check what address the recipients are replying to. So, get someone who’s external email is not working to send a message to an internet address of yours (maybe you have a Hotmail account or whatever). When you get the message click reply and see what address is will reply to. get back to us and we should be able to help some more.

Subject: User not listed in Domino Directory

Take a look at the location document on the users’ client software. Could be that they’ve got a bad Internet address on it.