Hi
 
I am using exchange server 2010
 
My offsite users connect via microsoft outlook using owa (http)
 
Problem is, they can send mail, no problem, but as soon as there is an attachment inserted, the mail does not leave their outbox.

This was working fine and all of a sudden just stopped.

Please help me

Hi,

As you said, I think that you are using Outlook Anywhere,not OWA(Outlook Web App);

I recommend you to troubleshooting your issue with the following steps

1. Please use OWA on browser to send a email with an attachment and check whether the recipient received the email.
2. Please try to change the pc to use outlook
3. Please try to connect Exchange using TCP/IP , not http;
4. Please keep your outlook version up to date.

Thanks.

Maybe there are some rules set.

So that the attachement is too big or attachements are generally banned.

Have a look for the ABPs