Problems to see same image messages from OWA

[Elvecio]

Hi People

I need a help Urgently!!!

At my environment there are one back end server, one Front End Server and in
the DMZ there is another Front End Server.
Well, There are SOME mails with pictures that we see normally inside the
company (LAN) by the back end or Front End server. BUT when we try to see it
from Internet (https) It's impossible. The OWA freeze when we try to view the
message..
I think the problem is relationship with the external Front End, but It's
strange because when I see my email from this server I get to open and see
the image mail. Only from Internet that it's impossible.

Have you already saw a problem like this? If you have any suggestion please
let me know.

Thanks very much