Mailer module roadmap: the path to beta and stable

Problem/Motivation

Once 📌 [PP-1] Add symfony mailer transports to DIC Postponed as a new experimental module has landed this issue will track the necessary work to get the module to beta and then a stable state.

Proposed resolution

Current status

• Currently (as of Drupal 11.1.x), a Mailer module based on the Symfony Mailer Component is proposed for core inclusion with experimental status. The module is located in core/modules/mailer.

Release Plan

📌 [PP-1] Add symfony mailer transports to DIC Postponed has been at RTBC since January 2025 and went through framework manager review early May 2025. It either could go into late 11.2 or early 11.3 branch. This will govern the schedule for a future stable version. Normally for Experimental modules, the module gets to Beta, which triggers including it in a release as an Experimental module. Then at a later date, it becomes Stable and gets the Experimental status removed.

Roadmap for Beta (experimental status)

Here is a list of sub-issues that we currently have for that phase, all of which are must-haves to make "Beta" quality, so we can keep it as a live Experimental module in a full Drupal release:

Mail delivery

• ✨ [PP-1] Ensure origin headers of mails sent using the mailer.transport service comply to RFC5322 Postponed
• 📌 [PP-1] Add a way to capture mails sent through the mailer.transport service during tests Postponed

Mail building

• 📌 Introduce theme negotiator for mail and use it in mail manager Active
• Decide on an approach on how mails are going to be built.

Roadmap for Stable

The schedule for stable release is not planned until mailer is in core as experimental.

To get this module to be ready for a stable release, here are some issues we'll need to resolve/finish, all of which are must-haves to make "Stable" quality:

Mail delivery

• Add configuration UI for the mail delivery layer.

Mail building

Non-stable-blocking issues