Glossary

Reply-To defined.

Reply-To is the email header that sets where replies go when that differs from the sender, so on a form notification hitting reply writes straight to the person who filled in the form.

Definition

How Reply-To works

Every email carries a From header naming its sender, and mail clients reply to that address by default. Reply-To overrides the default: when it's present, hitting reply addresses the new message there instead. The From address still identifies who actually sent the mail; Reply-To just names who the conversation belongs with.

Form notifications are the textbook case. The notification has to be sent from an address the service is authorized to send as. Sending "from" your visitor's address would fail SPF and DMARC checks, since the service doesn't own that domain, and land the message in spam. So the reliable pattern splits the two headers: From is the authenticated sending address, Reply-To is the visitor. You read the submission in your inbox, hit reply, and you're writing to the person who filled in the form, deliverability intact. FormWire sets this up on every notification, with Reply-To defaulting to the submitter's email field.

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