i set up my wifes gmail last night the automatic way (the wrong way) it downloaded all the messages first then when i sent receive all the messages disappeared, so i deleted the account i made and set it up the manual way (the right way)....
goto manila>email tab> new account (make sure the nice looking wizard pops open), enter your
user@gmail.com and password then
CLICK MANUAL SETUP. now all you have to do is change the incoming server to imap.gmail.com (dont worry about the ports i just overwrote them), change pop3 to IMAP4, click next and change the outgoing server to: smtp.gmail.com (this step may not be necessary cuz its already there), then continue on with the setup and it should work beautifully, if you are having more trouble connecting make sure your gmail account is
IMAP enabled in google settings