Quick Gotcha - Upgrading to Exchange Server 2007 with connected WinMo Activesync phones

OK - here's one that was very weird. I ran it past the DonK at TechEd, and he couldn't come up with an idea off the top of his head - had never seen it before.

We have an Exchange 2003 server. We've upgrading to an Exchange 2007 server - new server build and migrate the mailboxes across.

We have a number of WinMo smartphones - HTC Touch Diamonds and Palm Treo Pros. These are all connected to user mailboxes on the 2003 server.

I migrated my mailbox to the 2007 server, and edited the connection details on the smartphone to point it at the new external FQDN. Everything worked fine - mail would sync - happy campers. Because Exchange 2007 supports HTML mail, I flicked the switch across to HTML on the mobile client. This is where things started to go wrong.

Certain external emails (not all, but the certain senders/formats would do it every time) would sync to the Smartphone, with a blank body and a "click here to download the rest of this message" notification. Both server and smartphone had the sync size limits turned off, and anyway, the emails were quite often only 2k in size (forum update notifications for instance, with no attachments or embedded images). No amount of mucking around with either client or server settings would fix it. Set it back to plain text, and the entire messages would sync perfectly.

In desperation I broke the partnership between the device and the server, both on the device (removed the sync settings) as well as on the 2007 server (removed the device from my mailbox). Re-initiated the partnership from the device - same settings as before.

Now, it works perfectly.

So not quite the seamless upgrade that I was expecting, but we have a resolution. Unfortunately it means we need to schedule time with all our smartphone users once their mailboxes have been migrated. On the upside, their devices will still work fine in Plain Text mode following the upgrade, so we can schedule this at our leisure, and dangle the carrot of enabling pretty html mail for the users to encourage them to come see us.