What’s the difference between poor IP reputation and blocklisting?

Poor IP reputation results in gradual deliverability degradation. Mail might land in spam more often, get throttled, or face increased scrutiny. The provider is skeptical but not completely refusing your traffic.

Blocklisting is explicit rejection. Your IP appears on a published list that receiving servers query, and mail bounces immediately with specific error messages identifying the blocklist. Common lists include Spamhaus, Barracuda, and SORBS.

Poor reputation is a yellow flag. Blocklisting is a red flag with sirens. Recovery from poor reputation involves sending better mail. Recovery from blocklisting requires delisting requests and often proof that you have fixed the underlying problem.

Poor reputation is port authorities being suspicious of your cargo. Blocklisting is being banned from the harbor entirely with your ship's name posted at the gate.