Some users on our forum would like the option to force an amount of context in the notification emails.
I suggest this is implemented as a user-configurable option with a site default (shipped as 0).
The current situation as I understand it is that context is included if the user hasn’t received that post in an email yet. Therefore, if they receive every email (mailing list mode), they’ll never get context. This can be confusing if they delete emails after they’ve read them, because there’s nothing to refer back to if the new post references something in that previous post.
This is also related to the Reply by email requires reply at top feature request, if users include quotes to provide some context, then the email processing breaks.
The option would force Discourse to include the previous # of posts made in the topic.