I just *couldn't* figure out why my 7100 thought I had 4 unread messages (the little orange envelope, top left), even though I was sure I'd read everything I'd sent myself -- and the unit having only gone into service yesterday, I was pretty sure no one *else* had sent me anything...
If your Messages list is configured (in Phone Options->Call Logging) to display missed calls *those call records will show up in the count*. You have to Mark Opened on each call record to get the counter to clear.
Just another tip from Captain Obvious.
