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Overview The majority of e-mail providers today will use a type of DNSBL (Domain Name System-based Blackhole List) to prevent spam from affecting their users, while this helps keep your inbox clear it can affect you if you (or someone using the same mail IP) ends up getting your mail IP added to a blacklist. For information on how the DNSBL system works, please see our support article: Anti-spam solutions Getting Support When you have been added to a blacklist, e-mail you send to a company using that blacklist should be bounced back to your inbox, in this case you will need to provide our support with two main pieces of information:
  • The error message contained in the bounce back e-mail
  • The headers for the bounce back e-mail
Providing this information helps us determine if one of our servers has been blacklisted and start the process of having the IP removed from blacklists. Note: If you are using a mail IP not owned by ourselves we will not be able to assist with removing it from a blacklist, you will need to contact the owner directly (usually your ISP or another mail provider). Our support will be happy to assist with determining if you are using one of our mail IPs. If you did not receive a bounce back but your e-mail was not received by the recipient, it’s possible the mail was picked up by a spam filter. However if you still think your mail has been blocked, please contact support. Error Message
When you receive a bounce back e-mail, please look through the message for an error message with a 3 digit code (such as 550, 554) formatted similarly to this example: 
This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. The following address(es) failed:
e-mail@example.com

SMTP error from remote mail server after initial connection:
host mail.example.com 202.124.xxx.xxx:
554 Connection refused - IB115 202.124.xxx.xxx is blacklisted. If you believe this to be in error, please contact postmaster@example.com
The error on the last line contains both the IP the e-mail was sent from and the reason why the e-mail came back to you, when logging a case with support feel free to provide the whole bounce back message. E-mail Headers
While you have the bounce back e-mail open, please follow the steps on our article regarding viewing e-mail headers to gather the header information. The entire header will need to be provided when logging a case with support. Public Lookup
If you’re looking to check for yourself if your IP has been blocked or are looking for an update on the delisting process, you can check the IP in your bounce back e-mail against public lookup tools, some popular ones are: