iPhone mail does not pull entire message

Using an iPhone 3g, newest firmware. I think its 4.2.1.

I have two IMAP one POP and one Exchange (google app) accounts.

"MAIL" on my iPhone never seems to pull the entire message. This is annoying becuase when I get on the subway, I can't read my mail. Is there any way to have iPhone download the entire messages? These are short, 3 sentence text only emails that I am talking about... Very annoying. I am used to my old berry where all the emails were stored on the device...

Any ideas?

THANKS!