How to Check Mail Server Blacklists

Written by jeff orloff
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How to Check Mail Server Blacklists
Mail server blacklists help stop spam. (stop spam! image by Photosani from

As spam continues to flood e-mail boxes, network administrators are constantly looking for ways to stop spam and other junk mail from taking up space in the users' in-boxes and on the server. One common way to prevent spam from ever reaching an e-mail inbox is to blacklist the mail exchange (MX) record.

The MX record identifies the email server (computer) that is responsible for sending e-mail for a certain domain address. If the address is a known spammer, then the MX record can be blacklisted and anyone who relies on this blacklist will have mail from this sender's domain blocked.

Skill level:
Moderately Easy


  1. 1

    Identify the MX records of your e-mail account. The network administrator who is responsible for e-mail may have these records available. If you do not have access to them, you can use a service like MX Toolbox (see Resources) to look up this information for you.

    To perform an MX records look up using MX toolbox, go to their website and enter the domain name in the text box and then click on the MX Lookup button. The look up tool will then provide you with the host name and the IP address for your mail servers.

  2. 2

    Perform a search to see if the MX record exists on any blacklists. If the domain has been flagged as a sender of spam, odds are it has been blacklisted. Copy the IP address or the hostname from your records look up and paste it into the MX toolbox blacklist check (see Resources). Click on the button that reads "Blacklist Check." Your record will now be checked against more than 100 different blacklists. Any blacklist that your record shows up on will appear with a red dot next to it.

  3. 3

    Repeat the blacklist check for all recorded hostnames and IP addresses associated with your MX record. Most e-mail servers have multiple addresses or hostnames for redundancy and, while one may come up as clean, another may have been blacklisted.

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