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What is an IP Blacklist?

What is an IP Blacklist and how does it work?

What is an IP blacklist and how does it work?

IP Blacklists are real-time databases that identify IP addresses that are known to send spam or malicious content. They are defined by ISPs (Internet Service Providers) and specialized organisms and are used as references by email servers to determine if an incoming email can be trusted or not.

Email IPs that are blacklisted are likely to land in spam, as they have a history of negative behaviors.

Your IP has risks to be added to a blacklist if:

  • You have a high bounce rate (soft or hard) on emails you send.
  • You have a low engagement (open rate, answer rate, etc.) on emails you send.
  • You have a high proportion of emails sent that are flagged as spam by recipients.
  • You send emails into "Spam Traps" (inactive email addresses that are use to spot spam behavior and poor list hygiene).
  • Your IP is compromised, and used by spammers against your will.
  • Your IP is shared between multiple senders, that may use it to send spam.

Good sending practices and active authentication protocols (SPF, DKIM and DMARC) can help you to reduce the risks to have your IP blacklisted.

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