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POST
Inboxes are currently in private beta and only available to a limited number of users. The response shape might change before GA.Get early access if you’re interested in testing this feature.Once you have access, upgrade your Resend SDK to use the new methods:
Sends a reply from the inbox address right away, with no stored draft. The to recipients come from the message you reply to:
  • For a message the inbox received, the reply goes to its Reply-To addresses, or to its sender when it has no Reply-To.
  • For a message the inbox sent, the reply goes to that message’s to recipients.
Set reply_all to also copy the other recipients of the message. At least one of html or text must contain more than whitespace. The reply is threaded for the recipient. In-Reply-To is set to the Message-ID of the message you reply to, and References to that message’s References followed by its Message-ID. These headers can’t be set or overridden.

Path Parameters

Body Parameters

string | string[]
CC recipient email address. For multiple addresses, send as an array of strings. Without reply_all, the reply copies only these addresses. With reply_all, these addresses are merged with the copied recipients, without duplicates. cc and bcc combined must be fewer than 50 addresses. After the to recipients are added, the reply cannot exceed 50 recipients.
string | string[]
BCC recipient email address. For multiple addresses, send as an array of strings. BCC recipients of the original message are never copied.
string
The HTML body of the reply.
string
The plain-text body of the reply.
string
The subject of the reply. Max 2000 characters. Cannot contain a line break. When omitted, the thread subject is used, prefixed with Re: if it does not already start with it.
array
Files to attach, as on Send Email. Each one needs content or path. Up to 10 files. The content of all files can total at most 25 MB. A path file counts toward the 10 files only, because it is fetched when the email is sent. An empty file, a blocked file type, or a path that is not an http or https URL, or that points to localhost, returns a 422.
object
Custom headers to add to the email. Resend sets the In-Reply-To, References, and Reply-To headers, so you cannot set them here. Sending one of them, in any letter case, returns a 422. A header name cannot be empty, and names and values cannot contain line breaks or null characters, or the request returns a 422.

Headers

string
Add an idempotency key to prevent duplicated emails.
  • Should be unique per API request
  • Idempotency keys expire after 24 hours
  • Have a maximum length of 256 characters
  • A retry with the same key returns the first successful response, with the idempotent-replayed: true header
  • A failed request is not stored, so you can retry it with the same key
  • Reusing the key with a different body, or while the first request is still running, returns a 409
Learn more

Response Fields

string
The ID of the sent email. Use it with the emails endpoints.