What happens when an unknown person tries to post to my List?
All incoming email messages are verified against your list of approved Subscribers.
Emails from unknown addresses will have a rejection message returned. This rejection contains instructions on how to be added to your List.
Sometimes, your Subscribers may be emailing from a different address. For example, they signed up with a personal email but are trying to send from a work email.
In either situation, including instructions in the rejection message let's them know how to proceed.