Let me say this about that. Do you have your emails set on your computer to leave emails on the server? I had the same problem and when I spoke with VZW CS they reminded me I had to do that. I had to reinstall XP and of course it wiped out all my settings so I had to go do this again.
In OE there is a setting under Tools,Internet Accounts, Properties,Advanced Tab, at the bottom of box, select Leave a copy of messages on server and I selected 5 days in there. That fixed my problem.
Every few weeks I notice the lack of email on my Curve 8530. When I go into connections and check service status I will find that Blackberry Internet Service is not connected. I have to do what RalphT_Verizonsupport suggested and turn all connections off, wait a minute, then turn it back on. A few minutes later, a get dozens of emails.
What could be turning off my internet service? I am pretty sure my version is up to date.