Does being on one blocklist affect my reputation everywhere?

The impact of a blocklist listing depends entirely on which list and who consults it. Spamhaus listings have severe widespread impact because most major providers query it. A listing on an obscure blocklist may have minimal effect.

Different mailbox providers use different blocklists. Gmail and Microsoft run their own reputation systems primarily but do consult major external lists. Smaller providers and corporate gateways often rely more heavily on external blocklists.

Multiple listings create compounding problems. Being on several lists simultaneously suggests systemic issues with your sending practices. This broader pattern can influence providers who might otherwise have ignored individual listings.

Internal provider reputation systems also matter. Even without formal blocklist appearance, providers track your behavior and may filter accordingly.

A listing on one registry is a warning. Listings on many is a pattern that every harbor will notice.