You can clear the list of IP addresses authorized to send mail through your mail server at any time by following the steps below:
Click the Access Control link from the Mail Manager menu.
Click the Automatic Relay Authorization link.
A list of IP addresses that have been authorized by the POP Authentication method appears.
Click the Clear Relay List link to clear all IP addresses.
IMPORTANT NOTE:
Clearing the Automatic Relay List does NOT affect any Access Rules you may have put in place. Any Access Rule that specifies an address as a RELAY must be deleted directly from the Access Rules list (See Deleting Access Rules for instructions).