the reply_by_email_address is not used as the from address but the envelope-from, specifically so bounces work
Here’s an image that demonstrates how each address is used. The addresses themselves are specific to our hosting, but should be sufficient for an example.
notification_email: notifications@hs1.discoursemail.com
reply_by_email_address: incoming+%{reply_key}@hs1.discoursemail.com
A notification:
A replyable message:
