Swiftmailer has reached EOL in Nov '21

[enbrnz]

According to the core/composer.json core is using Swiftmailer

The Swiftmailer documentation states:

Swift Mailer will stop being maintained at the end of November 2021.
Swiftmailer is not maintained anymore. Use Symfony Mailer instead. Read more on Symfony's blog.

I would exepct ownCloud to use supported PHP components in case of security issues.

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 10 days if no further activity occurs. Thank you for your contributions.

[phil-davis]

Still needs to be done. composer reports:
Package swiftmailer/swiftmailer is abandoned, you should avoid using it. Use symfony/mailer instead.