As is mentioned in the latest post to his blog, Fabien Potencier has taken over as the project manager for the SwiftMailer project:

This is a great honor for me to take over such a project. The Swift Mailer project has been initiated by Chris Corbyn some years ago. He has done a wonderful job during the years, trying to find the best way to create a top-notch emailing solution for PHP. With the release of the 4th version of Swift Mailer earlier this year, I think we now have a very solid mailing library.

As a part of the effort to expand the use of the mailing library, it will become the default emailing solution for the Symfony framework. You can learn more about Swift Mailer from the project's website.