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IP Reputation

Email deliverability: How to check an ip reputation and protect your email deliverability ?

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par

Pierre-Yves
dans

A poor IP reputation can cause your emails to be classified as spam or even completely blocked by Mailbox Service Providers (MSPs).

Maintaining a good IP reputation is therefore essential—whether you’re sending transactional emails, newsletters, or marketing emails.

Why Your IP Reputation Matters

Just like in real life, a reputation takes time to build but can be lost in an instant.
Modern anti-spam filters (like those from Gmail, Outlook, or Orange) use behavioral and technical signals to determine whether an email sender is trustworthy.

Here are the main factors that influence an IP’s reputation:

  • Spam complaints rate: a high number of recipients marking your emails as spam negatively impacts your reputation—especially with Orange.
  • Bounce rate: invalid or inactive addresses indicate poor database hygiene.
  • Recipient engagement: open rates, clicks, replies… Gmail and Outlook closely monitor these signals.
  • Blacklist presence (RBL – Realtime Blackhole List): if your IP or IP range appears on one, your emails can be instantly blocked.
  • Sending volume: an IP with little history or low sending volume tends to have a weaker reputation than one that sends regularly without deliverability issues.
  • Volume variability: sudden spikes in email volume can trigger spam filters or reputation downgrades.

💡 Tip: for fluctuating volumes, using a shared IP can help maintain a more stable reputation.

How to Build and Maintain a Strong IP Reputation

Monitor Deliverability Continuously

Track your bounce rates, open rates, and spam complaint rates through your ESP or dedicated monitoring tools.

Follow Email Sending Best Practices

  • Send only to opt-in contacts.
  • Regularly clean your contact lists (remove inactive or invalid addresses).
  • Use proper email authentication: SPF, DKIM, and DMARC.

Warm Up Your IP Gradually

If your IP is new or rarely used, increase your sending volume progressively to build a solid reputation.

How to Monitor Your IP Reputation

1. Use IP Reputation Monitoring Tools

Here are the main tools for evaluating your IP reputation:

  • SenderScore (Validity): assigns a score from 0 to 100 based on email quality.
    → A score above 80 is considered good. Validity aggregates data from many ISPs through Feedback Loop partnerships.
  • Google Postmaster Tools: provides data on IP and domain reputation (The interfaces will soon no longer be available.), Gmail spam rates, deliverability errors, and domain compliance status.
  • Microsoft SNDS: helpful for monitoring IP reputation with Outlook and Hotmail users.
  • Cisco Talos (formerly SenderBase): offers a broad overview of your IP reputation across multiple networks.
  • Abusix: provides real-time alerts about spam or abuse incidents involving your IPs.
  • Barracuda Central: a simple tool for checking the reputation of an IP address.
  • Broadcom (Symantec): shows whether your IP reputation is rated good or bad.
  • Spamhaus: the global reference for blacklists. It also offers a reputation lookup tool and an API.
    Mindbaz has developed an open-source CLI interface to query the Spamhaus Intelligence API directly.
  • Trend Micro ERS: evaluates IP and domain reputation through their Email Reputation Service.

Check if Your IP Is Listed on Blacklists

An IP can end up on a blacklist when it’s associated with sending unsolicited or spammy emails.
The most well-known blacklists include:

  • Spamhaus (ZEN, SBL, XBL, PBL)
  • Spamcop
  • SURBL
  • UCEPROTECT
  • Invaluement
  • Barracuda RBL

Instead of checking each one manually, use aggregated blacklist checkers such as:

These tools test your IP against dozens of RBLs in a single scan and alert you if your IP is detected.

What to Do If Your IP Is Blacklisted

  1. Identify the root cause: spam complaints, poor database hygiene, server infection, or SMTP misconfiguration.
  2. Clean up your infrastructure:
    • Fix DNS records and email authentication (SPF/DKIM).
    • Check that no malicious scripts are sending emails from your server.
  3. Request delisting:
    Each RBL provides a form or contact method to request removal.
    Example: Spamhaus Block Removal Center
  4. Set up automatic monitoring:
    Tools like HetrixTools, Abusix, or custom API scripts can alert you instantly when an IP becomes listed.

Bonus: Automate IP Reputation Monitoring

If you manage multiple servers or sender IPs, automating blacklist and reputation checks is highly recommended.
Open-source and SaaS solutions like HetrixTools or Postmastery (for more complete monitoring) allow you to track your IPs, domains, and email deliverability performance from a single dashboard.