Swiftmailer will stop being maintained at the end of November 2021.
Please, move to Symfony Mailer at your earliest convenience. Symfony Mailer is the next evolution of Swiftmailer. It provides the same features with support for modern PHP code and support for third-party providers.
Swift Mailer is a component based mailing solution for PHP. It is released under the MIT license.
Swift Mailer is highly object-oriented by design and lends itself to use in complex web application with a great deal of flexibility.
For full details on usage, read the documentation.