I know it is not a perfect solution, but about a month or month and a half ago, I started missing messages, like, I would get 7 or 8 out of 10 messages, though the ones I received did come through on time. Couldn't figure out what was happeneing, and of course, Yahoo won't help, and T-Mo just wanted to blame Yahoo.
Then I saw that Yahoo now has a mobile phone app. It aint the best app in the world, seems to be pretty bloated, and lacks lots of the features that tru BB integration offers, but I downloaded it and used it anyway, so that I wouldn't miss any messages. They call is YahooGo.
I noticed today that I am missing messages again, so I just run the YahooGo app, and read and respond to the messages through that.
If it continues, I MAY be forced to switch to G-Mail, which seems to now reconcile like Yahoo, though with out the issues that Yahoo seems to be having lately. Do a search, you will see that they have been having slow and intermittant e-mail delivery for a couple of months now.