[meeting] 2026-02-04 core mailer beta planning

The revised approach of #3539651: Introduce email plugins is mostly complete and was briefly tested on a multilingual install. It isn’t trivial to import translations into a core main branch install - these steps need documentation so that reviewers can reproduce the setup.

The MR has a couple of threads open regarding the translatability of the default subject, these can be fixed easily.

In the current state of the MR, the rendering metadata is collected but then not used anywhere. The intention behind collecting the metadata was to allow contrib / custom modules to post-process the rendered result. The render metadata would be especially useful for CSS inlining. Since the post_render hook was removed a couple of iterations ago, there doesn’t seem to be any point of interception left where that could be achieved easily.

It was briefly discussed whether CSS inlining should be the responsibility of core or not. CSS inlining is likely a requirement for many sites as long as Outlook is still a thing. On the other hand, this probably requires adding external dependency to Drupal core. That process can be quite tedious. For the moment, we try to make it possible in contrib. The post_render hook should be restored and tested for its usefulness for that purpose.

For the weeks to come the main focus will be to get the MR into a mergable state. That requires work on documentation (doc comments and email.api.php), work on automated tests, conversion of the remaining core emails.

What’s next:

• Async communication in Drupal #symfony-mailer slack channel.
• Next planning meeting takes place March 4th 2026 at 4PM UTC+1.