What is IP Blocklisting?

If your company uses email marketing, IP blocklisting is something to try to avoid. Blocklisting occurs when your IP address (or the IP address you share with others) is ignored by a web hosting company, so that any mail you try to send is blocked and not forwarded.

The Definition of IP blocklisting

Blocklisting happens for any number of reasons, most typically when an IP address is suspected of sending spam. Continual blocklisting will affect your IP reputation because your IP address will be identified as a regular source of spam. Owners of an IP are responsible for what comes out of that IP address, so it’s important to stop spam from originating to avoid a reputation for spammy behavior.

There are hundreds of blocklists out there, so if you’re wondering “Who is blocklisting my IP?” you will need to do some research.

A blocklist is a list of IP addresses or domains that are known sources of spam; often referred to as DNSBLs (Domain Name System Blocklists). The technology was built on top of DNS and most MTAs can be configured to reject or flag messages that have been sent from a blocklisted IP. It’s important to remember that a DNSBL is a medium and not a specific list or policy. Policy in this context refers to the criteria that a DNSBL applies to decide which senders should be blocklisted and which shouldn’t. The policy also includes criteria for being delisted and the process for communicating with blocklisted senders.

There are two main types of blocklists; IP-based and domain-based. The IP-based lists include addresses of sending servers that are known spammers. Domain-based URI Blocklists (URI DNSBLs) are lists of domain names that appear within the email body. This blocklist will look for the URLs within the body of the email to see if it contains a domain that has been identified as a source of spam.

Dealing with a blocklisting issue

If your IP is blocklisted, all email traffic will come to a complete halt — even legitimate mail. You need to figure out how to get off blocklists quickly so email delivery is maintained for users.

Reliable email delivery is crucial for business operations. When it comes to IP blocklists, an ounce of prevention is worth a pound of cure. There are steps you can take to avoid email blocklists, which are recommended best practices to keep email traffic flowing.

Find out more about IP blocklisting, why it happens, and how you can prevent being blocklisted.


Related articles:


Eliminate email delivery problems caused by IP address blocklisting

MailChannels Outbound can help