Variables set in hook_mailer_build_build() are left out in the BodyEmailAdjuster

I believe it is a matter of timing.

BodyEmailAdjuster->build() runs with weight 400. It saves the variables into #context.

Your hook likely runs with default weight of 500. If you change your weight to 300 it should work.

Automatically closed - issue fixed for 2 weeks with no activity.

@adamps, can you expand on your answer? How do I change the weight? I am trying to set a variable inside HOOK_mailer_post_render but am getting an error saying "setVariable function is only valid in phases 0-1, called in 3.". I'm sure I also need to change post_render, but I cant find what to change it to.

To change the weight you need to use one of the other ways of doing a hook, see https://www.drupal.org/docs/contributed-modules/symfony-mailer-0/develop... → .

Currently you can't change variables in post-render. I agree it should be possible, there might already be an issue.