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.