Users not receiving mail outside our network

Hi, there are users who cannot receive mail from other users not on our network, there's about five, basicaly its an office without mail.I tried following up the DNS registration with the service provider but still nothing has come up. All the setting on the indivudual PC's are fine, the connection is fine but just cannot recceive mail from anyone outside the network.

 

Need a LOT more info!

 

Mail server details would be a start. What are you using (e.g. MS Exchange, ISP's mailserver)? How are you collecting mail (POP3 pull or SMTP feed)?

 

I hope i'll give you enough and not mix things up, Microsoft mail server, has linux on it ,pop3 incoming,smtp outgoing,cisco 2600 router.Then we have a line to the ISP. I checked this morning from the ISP's side and they they could see mail in one the users box but, she recieved that mail which was a test mail, but still insisted that she was not receiving any mail.
By the way I want to change my user name the one that I am logged in as, can I...

 

Hmmm. My guess is you don't actually have an internal mail server.

How are getting your e-mail? Are you using Outlook?

 

Sorry guys, its seems the domain was registered by another ISP, I'll have to find another domain for that office.

Otherwise, thanks a lot!