"Messages cannot be downloaded..."

[JohnnyOnTheSpot]

This has been happening randomly, but sometimes my phone just sits trying to receive headers...once the screen turns off it can't be turned back on until the error message pops up saying "messages cannot be downloaded to your phone..." This has happened a few times, and I'm testing it right now and it's doing the same thing. I'm running a stock Sprint 6.5 rom, and I'm using Yahoo mail, which has worked in the past on this phone...just randomly.