Field mapping

PostTo doesn't force your form into a fixed schema — send whatever field names you already use, and every one of them is stored exactly as sent. Four field names are also read for a second purpose: building the email PostTo sends on your behalf.

The four canonical roles

Default field name	Role	Used for
`subject`	Subject	Used as the outgoing email's subject line
`message`	Message	Used as the outgoing email's body
`email`	Reply-To	Set as Reply-To on the outgoing email, so replying goes straight to your visitor (also read from _replyto)
`name`	Sender name	Used to personalise the outgoing email and any autoresponder

If your form already sends fields named subject, message, email, and name, this happens automatically — there's nothing to configure. Fields with none of these names still get stored and shown in the dashboard; they're just not used to build the email.

Renaming the fields you already have

If your form uses different names — topic instead of subject, from instead of email — map them once under the endpoint's Settings → Field map. Each setting takes the field name your form actually sends:

Dashboard setting	Role it maps	Example value
Subject field	Email subject	`topic`
Message field	Email body	`body`
Email field	Reply-To address	`from`
Name field	Sender name	`fullname`

Mapping a role replaces its default field name — it doesn't add to it. If you map the subject role to topic, PostTo reads topic for the subject and no longer looks at a plain subject field, even if your form still sends one. Every field is still stored under its original name in the submission regardless of mapping — only which one fills the email's subject/body/reply-to/name changes.

Field mapping is available on the Starter plan and above. On the Free plan, only the default field names (subject, message, email, name) are read — see plans.

The Reply-To address

The email role has one extra fallback: if email isn't present or mapped, PostTo also checks a field named _replyto. Whatever value it finds is validated as a real email address — if it isn't one, it's simply left off Reply-To rather than rejecting the whole submission. Your form still delivers even if a visitor typos their email address.

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