Para ter certeza, suas informações de SMTP devem ficar assim:
# Correct configuration to get this working is:
config.action_mailer.smtp_settings = {
:enable_starttls_auto => true,
:address => 'smtp.gmail.com',
:port => 587,
:domain => 'whatever.yourrubyapp.com',
:authentication => :plain,
:user_name => '[email protected]',
:password => 'password'
}