When Discourse sends out Email notifications it includes a block of “Previous Replies”
This can be controlled on your user profile.
Out of the box we will include up to 5 posts at the bottom of email notifications provided we have not emailed them in the past.
If you are uneasy with that default you can change it to “never” send you previous replies, or “always” send you previous replies.
The default for all users can be controlled by forum admins,
default email previous replies
The number of posts included in previous replies can also be controlled using the
email posts context site setting.