I have had Mail for years. Have new MacBook Pro, set my old 3 accounts with Gmail, used them successfully. Yesterday, Mail rejected password to one of my accounts and does not accept it repeatedly. I entered this account from Gmail page, no problem, so my password is correct. Went back to Mail, this particular account is rejected. Checked all Mail preferences, all are the same as initially set. What is wrong?
MacBook Pro (Retina, 13-inch, Late 2012), OS X Mountain Lion (10.8.2)