There are different types of "listing" that applies to email.
Whitelisting - This means that any message from a specific IP address or domain name is to be accepted, regardless of the content.
Greylisting - This means that the IP address or domain name is currently not allowed to be accepted and will be rejected with a "try again later" message status.
Blacklisting - All emails sent from a certain IP address or domain name will be rejected due to past offences.
