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Plus addressing

published · September 13, 2026

Plus addressing is the convention by which mia+promo@ delivers to the same mailbox as mia@; the part after the plus is a tag the owner chooses, reported as is_alias and stripped in normalized_email.

Plus addressing, also called sub-addressing, is the convention most mailbox providers follow of delivering [email protected] to the mailbox of [email protected]: the part after the plus sign is a tag the owner chooses per signup, useful for filtering and for seeing who leaked an address, and invisible to the mailbox itself. Gmail adds a second rule of its own, ignoring dots in the username, so [email protected] and [email protected] are one inbox too.

What Spaw answers

is_alias reports a plus-tag, and normalized_email carries the canonical inbox with the tag removed and Gmail's dots folded away. Dedupe a list, key a suppression entry and count a repeat on normalized_email, never on the raw input, or one person becomes many. The alias weight is 5: a tag is a hint that a signup bonus is being farmed, not a fault.

What it does not mean

A tagged address is a real address, and the mailbox is verified like any other. The tag is the owner's, and a form that rejects it loses a careful customer rather than a fraudster.

Related

markdown version: /glossary/plus-addressing.md

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