A blacklist, also known as a blocklist, is a list of entities, such as email addresses, phone numbers, IP addresses, or websites, that are blocked from accessing a particular system or service. Blacklists are used for a variety of purposes, including preventing spam, malware, and phishing attacks.
There are a number of ways to check if an entity is blacklisted. One way is to use a blacklist lookup tool. These tools allow you to enter an entity, such as an email address, and check if it is listed on any blacklists. Another way to check if an entity is blacklisted is to contact the system or service that you are trying to access and ask them if the entity is blocked.