Create or send an email message
Queues, schedules, or sandbox-sends an email message. The legacy /v2/emails POST route
is a backward-compatible alias for this operation.
subject is required unless template_id is supplied. When using template_id, do not
also provide subject, html_body, or text_body; the template is rendered with
template_variables.
Note: template lookup failures (not found, wrong account) return 400, not 404.
Authorizations
Telnyx API key supplied as Authorization: Bearer <token>. In production, auth may be validated by the API gateway and forwarded via Telnyx auth headers.
Headers
Optional opaque, unquoted key for safely retrying the same logical request. Keys must contain 1 to 255 letters, numbers, hyphens, or underscores. Generate a unique UUID v4 for each operation and reuse it only when retrying that operation with the same request. Invalid headersโincluding duplicate, empty, malformed, or overlong valuesโreturn 400 with error code 10015. A request already in progress with the same key returns 409; reusing the key with a different request returns 422. Only successful responses are replayed, for up to 24 hours. Do not include sensitive data in the key.
1 - 255^[A-Za-z0-9_-]{1,255}$Body
Recipient email addresses must be unique across to, cc, and bcc after case-insensitive normalization. Duplicate recipients return 400 Bad Request.
1Optional display name for string from; overrides from.name when provided.
Reply-to address. If provided as an object with a name, only the email is stored; the name is ignored.
Required unless template_id is supplied. When using a template, the template's subject is rendered; if the template has no subject or renders empty, the request returns 400.
HTML email body. Returned only by GET /email_messages/{id}; omitted from create and list responses.
Plain text email body. Returned only by GET /email_messages/{id}; omitted from create and list responses.
Custom email headers. Write-only; not returned in responses.
Tags for categorization and reporting. Stored on the message and propagated to Email Detail Records. Not returned in API responses.
Optional unsubscribe-group UUID used for group-scoped suppression checks and unsubscribe handling.
When true, allows delivery to recipients whose suppressions explicitly
permit an override. Hard bounces, spam complaints, and invalid-address
suppressions cannot be overridden. Requires the email:override API scope.
Custom metadata. Write-only; not returned in responses.
Per-send open and click tracking overrides. Omitted properties inherit the sender domain's tracking settings.
Variables for Liquid template rendering. Non-object values may cause a 422 validation error on message creation, but are silently treated as an empty object for template rendering.
Future ISO 8601 time to schedule sending. Invalid or past timestamps
are silently ignored and the email is sent immediately. The legacy
alias send_at is still accepted for backward compatibility; when
both are provided, scheduled_at wins.
Deprecated alias for scheduled_at.
Telnyx message UUID of the message this send replies to. When provided,
the API sets RFC 5322 In-Reply-To and References headers on the
outbound MIME so the recipient's mailbox (Gmail/Outlook) threads it
correctly. The parent is looked up under the caller's account scope;
a UUID belonging to another account yields a non-enumerating 404.
Wire-only (Phase 1): the API sets the headers and does NOT resolve or
mutate thread_id on the server side. Messages sent without this
parameter are standalone (no threading headers injected).
Cannot be combined with forward_of_message_id (422).
Indicates a reply-all intent. In Phase 1 (wire-only) this does not
change the threading headers โ recipient selection is customer-
controlled (to/cc), and a thread is not defined by its audience.
When the referenced message has no thread context, reply-all
degrades to a plain reply (parent ID only in References). The
resolution engine (separate work) will expand the ancestor chain
at a later phase with no API change.
Only meaningful alongside in_reply_to_message_id.
Telnyx message UUID of the message this send forwards. Forwarded
messages start a NEW thread per RFC 5322 โ NO In-Reply-To or
References headers are set on the outbound MIME. The id is
recorded in the message's metadata for EDR provenance only.
The id is validated as a UUID but is NOT looked up against the
message store โ existence is the caller's responsibility (the
forward is pure metadata; it does not affect delivery). Cannot be
combined with in_reply_to_message_id (422).