A whitelist, which means only items on the list are let through whatever gate is being used.
A greylist contains items that are temporarily blocked (or temporarily allowed) until an additional step is performed.
Two blacklist monitors that check against all major and smaller blacklists are the following websites.
- www.mxtoolbox.com - If an IP address is listed, the listing will appear on top, in red. By clicking on it, the website for the blacklisting opens, and further instructions are provided there.
- www.blacklistalert.org – If an IP address is listed, it will appear so in red. If applicable, a URL is made available to go to the blacklist
