Exchange account throttles airport/congests my network.

Hi,

I have entered my work Exchange account details on my iMacs mail app. For some reason it congests my network. My internet slows to a crawl and it's only when I kill the mail app, does the speed return.

It did exactly the same thing when I tried to use Outlook for Mac-so may not be entirely Mac mail specific.

In truth-neither of the apps seem to be playing ball with my work Exchange account-emails take forever to arrive. Sent box doesn't show them as sent, for well over half hour or so. Its almost like it's in some kind of loop-chomping through network activity, but getting nowhere.

On my iPad and on the same network-everything works like a charm (same login details entered etc)

I'm on latest version of lIon, connect via Airport.

Anyone know what might be causing this? Any advice would be greatfully received.

Cos.