in your generated lib/model/doctrine/sfGuardUserTable.php add the following method:

public function retrieveByUsername($username, $isActive = true)
{
$query = Doctrine::getTable(‘sfGuardUser’)->createQuery(‘u’)
->leftJoin(‘u.Profile p’)
->where(‘u.username = ?’, $username)
->orWhere(‘p.email = ?’, $username)
->addWhere(‘u.is_active = ?’, $isActive)
;

return $query->fetchOne();
}

Thats it.. now your users can log in via email or via username. You can adjust the Doctrine query to your liking if you only want to allow emails.

sfDoctrineGuardPlugin calls that method from the validator, but you are just overriding it with a custom query.

from plugin documentation:

Validators
sfDoctrineGuardPlugin comes with a validator that you can use in your modules: sfGuardUserValidator.

This validator is used by the sfGuardAuth module to validate a user and password and automatically signin the user.