I replaced an old router with a new Draytek 2830 Dual WAN router. Immediately remote users started complaining that their Outlook was coming up with the "Connection to Microsoft Exchange has been lost" messages - that disappear after a few seconds.
I've tried various things -
Changing the load balancing settings so that all traffic from the Exchange server goes through WAN1 on the router
Changing the load balancing settings so that all traffic from the Exchange server goes through WAN2 on the router
Changing the external address for the outlook anywhere clients so that it comes in through WAN2
I'm pretty confident that it's something to do with the router - we never had these problems before. Having a little look around I'm wondering whether it's something to do with packet size? But we're getting to a technical understanding that's possibly out of my league