Linux Server Email Forwarding Fix

I'm doing some Perl/PHP development on a server running Red Hat Enterprise 5.2 and cPanel 11.23 which is having strange email forwarding delay problems that they are asking me to fix, but I'm not really up on that sort of thing to figure it out myself so I need some help. The emails that are being delayed are forwarding to an external exchange service, but seems to get hung up on the server for hours and sometimes days before forwarding. The email accounts and forwarding is being done in cPanel. I'm looking for an email system expert who can diagnose what exactly is causing the problem and fix it (assuming it's a problem with this server). If the problem is elsewhere (like the external Exchange service) the deliverable would be to provide evidence that the problem isn't on our server, otherwise the Exchange service will keep insisting that it's our problem and won't really look into it. Deliverables: 1. Initial diagnostic explaining what is causing the delays (email or Word document) 2. Fix the problem, if it's fixable OR 3. Documented proof that the delay is not occurring on our server