outlook 2007 is not allowing internal emails

[wa07]

We can receive external emails & can return emails to them but internal
emails on our company domain name can not be received to each other. Our
webhoster has confirmed this. And after completeing a matrix of tests
(including webmail with the same email address) it appears that it is Outlook
2003 & 2007 that is causing the issue. All email setting appear correct but I
need help???

 

[Roady [MVP]]

What were the results of these tests?
Which internal server are you using?
Which mail account type are you using?
Which error do you get when you try to send internally?

From the information provided, I doubt that it is actually an issue with
Outlook and expect it to be an issue at mail server level instead.