Aliases hide you. Knock prices you.

Some of the best inbox hygiene available today comes from alias services: Cloaked, SimpleLogin, Apple's Hide My Email. The pattern is elegant. You never give out your real address. Every merchant gets its own alias, everything flows into your normal inbox, and when one alias starts attracting garbage you kill it with one tap. As a bonus, the alias that leaks tells you exactly who sold you out. Rotation is a real defense, and these products do it well.

But rotation has a structural limit, and you feel it the day an alias falls into the wrong hands. An alias is binary. It is either open to everyone who has it, or it is dead. There is no middle state, no way to say: this address is public, and reaching me through it still requires being serious. Between the leak and the execution, the spam flows free. And your one truly public address, the one on your business card, the one ten years of correspondents already know, cannot rotate at all.

That is the layer Knock lives on. We do not hide your address. We price first contact with it.

Anyone may know thomas at knock dot email; a stranger who wants to reach me places a small refundable hold, like a hotel deposit. My real correspondents pass free forever. If the address leaks, nothing changes: the people who bought it still meet the gate. Leakage is an event for an alias and a non event for a bond.

The honest comparison cuts both ways, and we published the full table. Alias services protect your phone number today; we do not. They tell you who leaked you today; per service sub addresses are on our roadmap, and they will run on our own mail server, where no provider can quietly fold them back together. On the other side, an alias cannot stop a determined stranger, cannot make spam pay you, and cannot let an AI agent buy a priority review of its message. Different tools, different failure modes.

Which is the actual conclusion: these layers compose. Rotation defends you before the leak. The bond keeps defending you after it.

Use an alias for every signup form, and put a gate in front of the address you actually give to humans. The war on your attention has more than one front, and there is no rule that says you must fight with one weapon.

Thomas Ferriere, founder of Knock. The full comparison lives at knock.email/compare/knock-vs-cloaked.