Motorola Defy and Exchange ActiveSync

I’m working on a problem right now involving a Motorola Defy phone and Exchange 2003 Activesync. Posting this as a means of gathering my thoughts, and in the hopes that if anyone else if having this problem they find this for discussion.
About 15 of these phones have been brought in for our field staff since they’re rugged and reliable. We’ve broken too many HTC Desires out in the field to continue throwing away money like that.

The problem is, using the “Corporate Sync” application on the Defy, we can’t send email. Here’s what I know so far:

• Only using an Exchange connection, not POP3 or IMAP
• Attempting to send email over cell network fails
• Attempting to send email over wifi (on the same network as our Exchange server) is successful
• Attempting to send email over wifi (external network) fails (unconfirmed)
• The Defy reportedly used to work properly, but haven’t since mid-September
• This coincides with the network upgrades I made around that time, where I replaced our firewall with a Sonicwall NSA 2400 and replaced our Reverse Proxy (running Apache) at the same time.
• All Exchange traffic goes through the reverse proxy
• No other ActiveSync devices are having a problem (Windows Mobile 6.5, iOS, Android)

I’ve disabled all the security features on the Sonicwall in the hopes that was causing the problem to no avail. I’ve looked over the Apache logs on the reverse proxy, but don’t see anything unique to the Defy. I’ve compared my reverse proxy config between the new an old servers, with no difference.

This is frustrating because it seems to only be a problem with the Motorola Corporate Sync app, but its only a problem when traffic flows through my reverse proxy or firewall. Its such a specific set of circumstances and I can’t figure out what is causing it.

If I do come upon a solution, I’ll definitely post an update.