So…I had the hardest time getting my iPhone 4’s mail client to access my Gmail. Come to find it was mainly to do while on a wireless network (my work was not allowing smtp.gmail.com to be accessed for some reason.
To resolve this, I removed the account completely and started from scratch. Go to your Settings >> Mail… >> Add >> and choose ‘Exchange’. Enter you login info (full email address as the username) and for the server (when prompted) put in ‘m.google.com’ and BINGO!
Hope this helped others besides me!
Of course…this may be kind of useless now that Google has finally released a native Gmail app for the iPhone…oh well. =)