When Discourse sends out email notifications, it can include a block of “Previous Replies”.
This can be controlled on your user profile by the Include previous replies at the bottom of emails user setting. Out of the box we don’t include previous replies in email notifications; instead we include an excerpt of the post being replied to at the bottom of the notification. So the default for the Include previous replies at the bottom of emails user setting is never:
You can change it to always, or to unless previously sent, to receive previous replies unless they were already sent in a previous email.
By default, we will include up to 5 posts at the bottom of email notifications, provided we have not emailed them in the past. This number can be changed using the email posts context site setting.
Whether to send previous replies in emails can be controlled by forum admins using the default email previous replies site setting. When changing this setting, you will have the option to apply the change historically to all existing users, or to new users only.
(Admins can also control whether to include the excerpt of the post being replied with the default email in reply to site setting.)