--- title: Runtime API description: Email Workers Runtime API reference for handling, forwarding, rejecting, and replying to incoming emails. image: https://developers.cloudflare.com/dev-products-preview.png --- > Documentation Index > Fetch the complete documentation index at: https://developers.cloudflare.com/email-routing/llms.txt > Use this file to discover all available pages before exploring further. [Skip to content](#%5Ftop) # Runtime API ## Background An `EmailEvent` is the event type to programmatically process your emails with a Worker. You can reject, forward, or drop emails according to the logic you construct in your Worker. --- ## Syntax: ES modules `EmailEvent` can be handled in Workers functions written using the [ES modules format](https://developers.cloudflare.com/workers/reference/migrate-to-module-workers/) by adding an `email` function to your module's exported handlers: JavaScript ``` export default { async email(message, env, ctx) { await message.forward(""); }, }; ``` ### Parameters * `message` ForwardableEmailMessage * A [ForwardableEmailMessage object](#forwardableemailmessage-definition). * `env` object * An object containing the bindings associated with your Worker using ES modules format, such as KV namespaces and Durable Objects. * `ctx` object * An object containing the context associated with your Worker using ES modules format. Currently, this object just contains the `waitUntil` function. --- ## Syntax: Service Worker Service Workers are deprecated Service Workers are deprecated but still supported. We recommend using [Module Workers](https://developers.cloudflare.com/workers/reference/migrate-to-module-workers/) instead. New features may not be supported for Service Workers. `EmailEvent` can be handled in Workers functions written using the Service Worker syntax by attaching to the `email` event with `addEventListener`: JavaScript ``` addEventListener("email", async (event) => { await event.message.forward(""); }); ``` ### Properties * `event.message` ForwardableEmailMessage * An [ForwardableEmailMessage object](#forwardableemailmessage-definition). --- ## `ForwardableEmailMessage` definition TypeScript ``` interface ForwardableEmailMessage { readonly from: string; readonly to: string; readonly headers: Headers; readonly raw: ReadableStream; readonly rawSize: number; public constructor(from: string, to: string, raw: ReadableStream | string); setReject(reason: string): void; forward(rcptTo: string, headers?: Headers): Promise; reply(message: EmailMessage): Promise; } ``` An email message that is sent to a consumer Worker and can be rejected/forwarded. * `from` string * `Envelope From` attribute of the email message. * `to` string * `Envelope To` attribute of the email message. * `headers` Headers * A [Headers object ↗](https://developer.mozilla.org/en-US/docs/Web/API/Headers). * `raw` ReadableStream * [Stream](https://developers.cloudflare.com/workers/runtime-apis/streams/readablestream) of the email message content. * `rawSize` number * Size of the email message content. * `setReject(reasonstring)` : void * Reject this email message by returning a permanent SMTP error back to the connecting client, including the given reason. * `forward(rcptTostring, headersHeadersoptional)` : Promise * Forward this email message to a verified destination address of the account. If you want, you can add extra headers to the email message. Only `X-*` headers are allowed. * When the promise resolves, the message is confirmed to be forwarded to a verified destination address. * `reply(EmailMessage)` : Promise * Reply to the sender of this email message with a new EmailMessage object. * When the promise resolves, the message is confirmed to be replied. ## `EmailMessage` definition TypeScript ``` interface EmailMessage { readonly from: string; readonly to: string; } ``` An email message that can be sent from a Worker. * `from` string * `Envelope From` attribute of the email message. * `to` string * `Envelope To` attribute of the email message. ```json {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/directory/","name":"Directory"}},{"@type":"ListItem","position":2,"item":{"@id":"/email-routing/","name":"Email Routing"}},{"@type":"ListItem","position":3,"item":{"@id":"/email-routing/email-workers/","name":"Email Workers"}},{"@type":"ListItem","position":4,"item":{"@id":"/email-routing/email-workers/runtime-api/","name":"Runtime API"}}]} ```