This article explains the significance of IP blacklist checks in DMARC (Domain-based Message Authentication, Reporting, and Conformance) reporting, specifically for customers using email services like but not limited to SendGrid, Mailchimp, Sendinblue, and HubSpot - these checks are run on all sending IPs. 

What is DMARC Reporting?

DMARC is an email validation system designed to protect your domain from unauthorized use, such as email spoofing or phishing. It allows domain owners to decide how their email is handled, providing a way to report on email delivery issues.

Why We Check the IP of Sending Services

Our tool acts as a monitoring system, processing the DMARC reports we receive in XML format from the recipients' mail servers. When we parse these reports, part of our service includes checking if the IP address of the email sending service (like SendGrid or Mailchimp) is listed on any blacklists.

The Role of Blacklists

IP blacklists are used to identify IP addresses that may be involved in spam or malicious activities. Being listed on a blacklist can affect email deliverability and reputation.

Our Process

  1. Data Reception: We receive DMARC reports from email recipients' servers.
  2. Parsing: We parse these reports to extract relevant data, including the sending service's IP address.
  3. Blacklist Check: We cross-reference these IPs against known blacklists to identify any potential issues.

What Happens If an IP Is Blacklisted?

If we find that an IP address from your email service provider is on a blacklist, we will notify you. This information is crucial for the following reasons:

  • Awareness: It helps you stay informed about potential deliverability issues.
  • Actionable Insight: You can take steps to address these issues, such as contacting your email service provider.

Next Steps if Your IP Is Blacklisted

If you find that an IP from your service is blacklisted, consider the following actions:

  1. Contact Your Provider: Reach out to your email service provider to inform them about the blacklisted IP.
  2. Inquire About Solutions: Ask if it's possible to route your emails through a different IP or if there are other remedies available.
  3. Discuss Impact: Discuss with your provider whether the blacklisted IP could be affecting your email deliverability.


Our role is to provide you with accurate and timely information regarding your email sending IPs and their status on blacklists. While we don't control these lists or the IPs, we aim to empower you with the information needed to maintain the best possible email deliverability and reputation.