Public blacklists are created by large, trustworthy companies, as well as small, independent networks. But since anyone can create a blacklist, they don’t all have the same impact on deliverability. Mailbox providers and filtering companies do not leverage every blacklist in making inbox placement decisions. Instead, they typically combine data from various public blacklists, as well as data from their own networks, to determine your credibility as a sender.
Email marketers often associate blocking with being blacklisted. It’s important to note that blacklist providers are not the ones blocking your mail—it’s the mailbox provider leveraging your blacklist status that blocks your mail. If landing on a blacklist does lead to having your mail blocked, focus on the potential causes for the listing. Blacklisting is most often caused by poor list quality and end user complaints.
There are two types of blacklists: IP address-based and domain-based.