Issues with Exchange 2013 load balancing through LTM (v11.6)

Hi Chris-

I'm sorry you're having issues with your Exchange deployment.

Off the top of my head, without looking at your case notes directly (which I'll do), it sounds to me like there's a strong possibility that you have a duplicate IP address on your "external" VLAN--meaning, your virtual server shares an IP address with something that already exists. That would explain a lot of things: the intermittent connectivity on the same L2 network, the ARP issues, the working connectivity from remote networks (because the intervening router already has a good ARP table entry, or hides the problem by trying repeatedly to get a good connection), etc. Can you move your Exchange virtual server(s) to an entirely new IP address on the same VLAN/subnet and let us know what happens?

On a separate note, we've made a conscious decision to keep SMTP as a separate entity/iApp for now, in part for reasons of not complicating the iApp any more, and in part because many/most of our customers use a 3rd-party SMTP relay or appliance on their DMZ to send and receive SMTP messages, and don't rely on Exchange itself for that. Yes, eventually there needs to be a Send and Receive connector somewhere in the Exchange environment, but BIG-IP doesn't necessarily sit in front of those connectors. In the future, we may incorporate SMTP directly into the Exchange CAS iApp, or allow the two iApps to be optionally "chained", but we haven't made a final decision on that yet.