How to detect IP rotation abuse?

IP rotation abuse is when senders rapidly cycle through IP addresses to evade reputation systems. When one IP gets blocked, they switch to another, playing whack-a-mole with blocklists. Mailbox providers and blocklist operators watch for this behavior.

Detection signals:

Similar content across IPs: Same templates, same links, same From addresses appearing from multiple IPs suggests coordinated evasion.

Shared infrastructure fingerprints: Headers, DKIM selectors, tracking domains, or other technical signatures that link different IPs to the same sender.

Sequential IP usage: Addresses from the same subnet appearing one after another as each gets blocked.

Volume displacement: When one IP stops sending and another immediately picks up similar volume to the same recipients.

Short IP lifespans: Legitimate senders use IPs for months or years. Abusers burn through IPs in days or weeks.

Blocklist operators like Spamhaus list entire IP ranges when rotation abuse is detected. They also track domains and content, so switching IPs doesn't help if your domain or message patterns are flagged.

Changing ships doesn't help if you're flying the same flag and carrying the same contraband.