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What is a blacklist?

What is a blacklist?

A blacklist, alternatively called a DNSBL(DNS blacklist) or RBL(Realtime Blacklist), is a spam blocking list that can prevent a mail server from sending email.

Where should I check for IP blacklisting?

There are hundreds of DNSBL sources across the internet which can cause confusion about what affects email deliverability. The following major DNSBL providers are monitored and considered reputable by us and other services :

  • SpamHaus - One of the largest and most reputable DNSBL. SpamHaus is used by the majority of ISPs and email service providers.
  • SpamCop - A DNSBL which is based off reports by SpamCop users.
  • Barracuda Reputation Block List - Open source DNSBL service.
  • Invaluement - A IP and domain subscription based anti-spam blacklist.

How can I detect if delivery is affected by a blacklist?

Mailgun provides event logs for tracking for each message sent through our service. The event logs are available by logging into the control panel and clicking on ‘Logs’ at the top. Alternatively, event logs can be requested through our Event API. We will provide failed events when an email could not be delivered to the recipient email server. Clicking the log event will expand the view for more details of the event.

I detected failures due to blacklisting. What are the next steps?

First, there's a high chance we've already processed the delisting and awaiting confirmation of removal from the DNSBL. Each DNSBL processes removal differently and vary in time range. To check on the status or request further investigation of a failed event, contact our support team and please include the full log details.

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