This setting determines how long someone who has applied for membership but not been approved by an administrator should remain until they are permanently erased from the system. By
default, un-approved members are never purged. You can specify any number of days (from 1 day to 1 year) before they are erased.
This setting only applies if the mailing list has its security set to "private", so that new memberships require administrator approval. See Subscription Security.