First, I'm most definitely not an andoid expert - I don't even have one to tinker with...
I've got a user with a verizon HTC Thunderbolt who connects to an Exchange 2003 server for email and contacts. It works well, with one exception (besides lousy battery life):
It seems that every Sunday, at some time, all emails older than a week old are removed from the device. They are NOT removed from the exchange server and are visible in OWA and within Outlook. There are lots of windows phones that connect to this same exchange server without this problem so I don't believe it's anything on the server side.
I had the user go into messaging, then settings, scroll down to "Delete old messages" and confirm that the box wasn't checked, which it wasn't.
I've googled like crazy, but all I find is this:
which doesn't say much other than it being a "known verizon issue" - I don't know anything about the reliability of that poster though.
The user called Verizon but was told that there's nothing wrong with the phone (not exactly answering the question...).
She doesn't think that there's any backup applications running that could be deleting the messages.
Any suggestions or insights would be greatly appreciated.