I have a client that would like to customize (read: insert ads into) outgoing all-mail and daily-summary emails for people in mailing list mode and the since-your-last-visit email. “Go ahead” was my knee-jerk reaction, but it seems that those messages somehow are not in the list of templates in /admin/customize/email_templates.
This thread from a year ago asked a similar question.
Is the easiest/best way to customize those messages to write a plugin?
It would be nice if when a feature post was added it included what version added the feature. Though lots of folks are on tests-passed, many are on stable for various reasons and it’s confusing when you go looking for something and it’s just not there.