End of maintenance of Swift Mailer | Change php mailer library

[Swift Mailer](https://swiftmailer.symfony.com/docs/introduction.html) is no longer maintained as of November 2021. Switching to a newer / maintained library is desirable.

Possible packages 
- PHPMailer [GitHub](https://github.com/PHPMailer/PHPMailer)
- Symfony's Mailer [GitHub](https://github.com/symfony/mailer) [Docs](https://symfony.com/doc/current/mailer.html)