I know what the problem is:
Follow these instructions:
Start, Settings, Connections Tab at the bottom, Connections (the Icon), Advance Tab at the bottom, then Select Network.
The first box will say programs that connect to the internet should connect using blah blah blah. Keep a mental note of what the first box says.
Go to your Gmail inbox and click on Menu, Tools, Options. Tap on the Gmail account to edit the settings. Keep hitting next until you get to the Outgoing Email server settings. Once there click on Advance Server settings at the bottom. Make sure the network connection matches the one listed in that first box I told you to keep a mental note of ok. After you make the change hit done and next to finish out. Try to send/receive. Let me know if this helps.