insite email problem

[Jeff]

Hi all,
I work at a company as a consultant and check my email outside the
office. I receive email and can send email correctly using Outlook
but can't receive email from people inside the company.

In fact, everybody working there can't send email at each other or at
themselves.

They can send email outside (hotmail, yahoo, etc)
They can receive email from outside.

The only problem is that they're unable to receive email from their
own teamates (ex : (e-mail address removed)).

Do you have any idea of the problem???

Thanks in advance

 

[Jeff]

I did some test today, and I don't get it...

I can send an email outside, receive email and all work fine if I use
the webmail portal of the hosting.

I configure Outlook with my email adress at the company and get the
same problem they get... And if I send an email from the webmail
portal, Outlook is able to get it...

So the problem is really when he send his email (and the email appears
in the sent mail folder). But I don't understand why they can send
email to others and not someone in they office... Since it's a small
company, they don't use server and are just connected by some
hub/switch.

Do you have any idea of the problem?