yii\mail\MailerInterface::sendMultiple PHP Метод

This method may be implemented by some mailers which support more efficient way of sending multiple messages in the same batch.

public sendMultiple ( array $messages ) : integer
$messages	array	list of email messages, which should be sent.
Результат	integer	number of messages that are successfully sent.

    public function sendMultiple(array $messages);

MailerInterface