Relay Domains

A relay service gives someone a stand-in address that forwards to their real mailbox. The sender never learns the real address, and the owner can switch off a stand-in at any time without affecting the mailbox behind it. Apple's Hide My Email, DuckDuckGo Email Protection, Firefox Relay, and SimpleLogin all work this way.

relay_domain is true when mail for the checked domain is handled by one of these services. That covers the service's own domains, and also a domain of your own whose mail is routed through a forwarding service, since the effect is the same either way: the address you were given is not the mailbox the mail ends up in.

The field is returned by the domain and email endpoints, and is available in Gates as domain.relay_domain.

Examples

Domain	relay_domain	Why
privaterelay.appleid.com	true	Apple's Hide My Email
duck.com	true	DuckDuckGo Email Protection
mozmail.com	true	Firefox Relay
gmail.com	false	A public mailbox provider, not a forwarding service

Your own domain can be flagged

relay_domain describes how a domain's mail is currently handled, not who registered it, so an ordinary company or personal domain is flagged while its mail is routed through a forwarding service. This catches people out most often when a registrar or DNS provider turns email forwarding on by default and the owner never set it up deliberately.

The flag follows the current setup. A domain that stops forwarding, by moving to a hosted mailbox or a self-hosted mail server, is reclassified. If you believe a domain is flagged incorrectly, submit it for review.

What a relay address hides

Mail sent to a relay address reaches a real person who reads it, so the address is deliverable in a way that an address on a domain with no MX records is not. What the relay conceals is which mailbox is behind the address, and whether two addresses belong to the same person.

Relationship to disposable domains

A disposable address expires on its own and its mail is discarded. A relay address stays live and forwards to a mailbox the owner still reads, until they choose to disable it. disposable and relay_domain are separate fields, and each answers only its own question. See Disposable Domains.

A forwarding service that handles a domain's mail also appears in mx_providers with a type of forwarding. See MX Providers.

For background on how forwarding works, see What is Email Forwarding.