The Symfony Mailer component was released for the first time in Symfony 4.3, released in May 2019. Since then,
we have worked on improving it by adding more third-party providers and adding some missing features that were already available
in Swiftmailer, like DKIM support and email signing.
As of Symfony 5.3, all Swiftmailer great features and more are available in Symfony Mailer.