How to set up a mail server on plesk?

Question

Yii

There is a VDS (centOS) on it a plesk panel. According to totorials, everything is so simple, but it does not work. In the server settings, for some reason, the domain.com mail server, although intuition suggests that it should be mail.domain.com.
Here is the config for swiftmailer:

'mailer' => [
            'class' => 'yii\swiftmailer\Mailer',
            'useFileTransport' => false,
            'viewPath' => '@common/mail',
            'htmlLayout' => '@common/mail/layouts/html',
            'textLayout' => '@common/mail/layouts/text',
            'transport' => [
                'class' => 'Swift_SmtpTransport',
                'host' => 'domain.com',
                'username' => '[email protected]',
                'password' => 'точно правильный',
                'port' => '25',
            ]
        ],

The send script works without errors, but returns false. The logs are empty. Push in the right direction.