Do not mandate symfony mail Drupal module

[Eli-TW]

The localgov_workflows_notifications submodule mandates the use of the Drupal symfony_mailer module.

This causes the following problems:

• this causes this module, and then by extension the site, from being able to use the GOV.UK Notify service and Drupal module. This prevents a significant proportion of the local gov target audience using a potentially free email service in tandem with this module
• drupal/symfony_mailer is loaded by composer when the base localgov_workflows module is installed, whether they are using it or not.

We should remove the hard dependency on drupal/symfony_mailer, list it as a recommendation, and fallback to Drupal's mail system if it is not present.

[Eli-TW]

Linking relevant drupal issue: https://www.drupal.org/project/govuk_notify/issues/3501781

[stephen-cox]

Workflow Notification uses Symfony Mailer for more than just email sending. It also uses the email templating and class based email sending (doing away with hook_mail). So removing Symfony Mailer requires a reasonable rewrite.

Symfony Mailer is plugable so it should be possible to write a transport plugin to use the Gov Notify service.

[ekes]

Discussed this with @Eli-TW and others at Drupal Dev Days. Sadly the Symfony Mailer module developer has gone out alone and hasn't got traction for his implementation. Drupal Core is going to move very very slowly, but not in this direction. The templating, transport switching, symfony mailer option taken by Drupal CMS being the likely direction. So sadly we may well need to do the not inconsiderable work of unpicking this one at some point.

[NikLP]

Is there any value in assessing what the https://www.drupal.org/project/symfony_mailer_lite module offers with a view to swapping this out with the aforementioned?

Furthermore any pointers to where the unpicking needs to occur would be a seemingly valuable asset on this thread I suspect?

[Eli-TW]

@NikLP I don't think symfony_mailer_lite helps directly with getting localgov_workflows to work with govuk_notify, as again, they fulfil the same function.

However, it may be useful to use symfony_mailer_lite as a swappable default, where govuk_notify could be used instead. And then use https://www.drupal.org/project/easy_email for the templating that localgov_workflows currently uses the symfony_mailer module for.

symfony_mailer_lite + easy_email is the combination used by Drupal CMS and is what @ekes is referring to in #131 (comment)

Note I haven't tested easy_email with govuk_notify yet!

[NikLP]

I didn't mean SML as an immediate fix for the GN problem, more that the SM module is a bit clunky and would SML be a viable alternative in LGD with less unpicking work if it were a simple(ish) swap between the two.

Definitely value in looking at the DCMS solution as I've alluded to elsewhere before now, as obviously this somewhat defines (via a potential de facto standard) how Drupal in general may approach mail handling in future.

[andybroomfield]

Would using hook_mail and then skipping it if it detects that symfony mailer is installed work here?

[stephen-cox]

I see Drupal core is now shipping with en experimental Mailer module based on the Symfony Mailer library: https://www.drupal.org/node/3519253. It would make sense to use that, but it is only in Drupal 11 and the change record states the API may change, so we'll need to wait for it to become a bit more stable.

[NikLP]

There are some threads re symfony mailer in core here, in #symfony-mailer:
https://drupal.slack.com/archives/C06MG01QS3X/p1746722228240199
https://drupal.slack.com/archives/C06MG01QS3X/p1747066871385969