I recently had trouble sending emails with phpmailer using google smtp.
Basically I had this problem
PHPMailer - SMTP ERROR: Password command failed when send mail from my server
which I solved thanks to this post
moreover, this article was helpful too
https://accounts.google.com/b/0/DisplayUnlockCaptcha
and even more important was to: sign out of any Google accounts, close your browser and log back in
Have a nice day.
Stefano Somaglia