What are email blocklists?

Excerpted from ConvUrgency.com's Smart Email Marketing Guide

Blocklists are the bane of many an email marketers' existence. Blocklists are exactly that – a list of domains/senders which are blocked (they are interchangeably referred to as blacklists). There are public blocklists that businesses can reference, most large businesses and ISPs also have their own blocklists, and even subscribers themselves can have their own 'blocklist', depending on their email client. Obviously, we're more concerned about the larger blocklists, because those are the ones that can prevent us from reaching a large portion of our subscriber base.

Contrary to the purpose of a blocklist – you do not have to be a spammer to get on one. Your email may trip one of the many flags on the spam filters of a blocklist. Or enough people may report you as spam (even undeservedly), and you'll be blocked. Even if you send over a certain threshold of emails to one domain in the span of one hour, you could end up blocked.

So be careful! Set your domain threshold within your ESP. Allow people to unsubscribe. And test your emails for spam content before you send them.

If you end up on a blocklist, it can be quite an ordeal to get off, requiring proof of authenticity, and various levels of approvals. Fortunately, some anti-spam solutions reference blocklists as only one component in determining if a message is spam, so you may not always be blocked for wrongly being on a blocklist.

You may not always know when you've been placed on a blocklist. Sometimes you will indeed receive an alert or bounceback, but more often your emails will just be swallowed up, or 'blackholed'. To figure out if this is happening to you, monitor your domain-delivery reports. If you see that you've sent 100 emails to a domain, there were no bounce-backs, but there were 0 opens, then you're most likely blackholed, and you need to email the system administrator to get off their blocklist.

Excerpted from ConvUrgency.com's Smart Email Marketing Guide