How Temporary Emails Work: A Technical Overview

Disposable email feels like magic — you type a random local part, mail arrives, and the address evaporates an hour later. Underneath, it is plain old SMTP plus a couple of clever tricks.

The catch-all domain

A disposable email service owns one or more domains. Its DNS MX records point at its own SMTP server. Crucially, that SMTP server accepts mail for every local part — anything@the-domain — rather than only known mailboxes. This "catch-all" behaviour is what lets users invent fresh addresses on the spot.

Receiving mail

When a sender deposits a message, the SMTP server parses the envelope, extracts the recipient, and stores the message — often in Redis with a TTL — keyed by the local part. There is usually no real mailbox; everything is ephemeral.

Showing it to the user

The frontend polls the API or, more commonly, holds an open connection (Server-Sent Events or a WebSocket). When the SMTP server stores a new message, it publishes an event; the frontend renders it within a second.

Expiry

The TTL on the storage key is the entire expiry mechanism. After it elapses, the inbox simply stops existing — the next request returns 404 — and the storage entry is reclaimed. Simpler than it looks, and almost free at scale. Developers can drive the same flow programmatically through our public API.