Since july 2014, Gmail changed the default security settings for new account created, now it blocks all access and you receive a message in Automatic Email Manager that your login or password is invalid.
You have to enable the third party connection in your Gmail account, like explained below...
Note: We plan to include the latest Gmail authentication in futur version of Automatic Email Manager.
If you continue to receive the message in Automatic Email Manager that login or password is invalid, you should change the Gmail password to reflect changes. Just go in the Gmail account, Security then Password and change password, it should work fine now.