A limit for the list allows you to prevent members from receiving email if they have received the amount of mail in the number of preceding days that you specify.
Refer a Friend
Allows list members to refer or invite others to yours list.
You may track how many friends were referred by list members, how many opened or clicked on a tracking link in the invitation, and how many ultimately joined the list.
Select how many days/weeks/months apart a mailing will run.