What is a blocklist or realtime blocklist (RBL)

It’s a list of IP addresses where mail servers do lookups and block email coming from IPs on this list.  It’s done through DNS lookups which is good to know for testing but with your mail server software you will just have to configure it properly to use the blocklist.

Even if you don’t use a blocklist, you can be affected by them if your mail server IP address gets on their list.

 

Which blacklists are reputable?

There’s a lot out there. Some are small or very specific to maybe just a country. Some even want cash to get off their list faster which I have issues with especially since the person on a blacklist often is a victim of a compromise of some sort. If they weren’t and they were a spammer why would you let them off your list? You wouldn’t.

I’m just going to list the ones I would use or consider to be reputable and some details on each.

 

Barracuda

Lookup URL: http://barracudacentral.org/lookups

Notes: They can be quick to block email from you if they see spam but they are also quick to remove you one you put in a delist request which you must do.  Usually delisted within hours of submitting your request.

SPAMHAUS

Lookup URL: https://www.spamhaus.org/lookup/

Notes: Good blocklist. I have used them for their blocklist on email servers and recommend them

 

Blocklists I’m not thrilled with

 

 

 

Senderscore

Lookup URL: https://www.senderscore.org/blacklistlookup/

Notes: Don’t like that they want to get info to market to you just to do a lookup. I could understand if they would just ask for this when delisting however.