Glossary · Email

Reply-To Header

The Reply-To header names the address replies should go to when it differs from the From address, so answers reach a monitored inbox or help desk.

Updated October 6, 2026

The Reply-To header is an optional email header that tells the recipient's client where to send a reply. If it is absent, replies go to the From header address.

Why it matters

It lets a message be sent from one address while replies reach another: a newsletter sent through a platform can send from news@example.com and have replies go to support@example.com. It is separate from the envelope sender, which handles bounces. Reply-To is also abused: scam emails often use a harmless-looking From and a Reply-To that points at the attacker, so mismatches are a warning sign.

Example

From: Example Shop <orders@example.com>
Reply-To: Example Support <help@example.com>
Subject: Your order has shipped

Pressing Reply fills in help@example.com. Some systems set Reply-To to the sender's own address when a contact form sends mail from a website's domain, so the owner can answer the visitor directly.

Common mistakes

  • Setting Reply-To to a domain with no mailbox, so replies bounce.
  • Putting the visitor's address in the From header on a contact form, which fails DMARC; use your domain in From and the visitor in Reply-To.
  • Ignoring a Reply-To that differs from From in unexpected mail.

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