Sending and Receiving Mail with the Mail API

This guide describes how to use the Mail API to send and receive mail.

This API is supported for first-generation runtimes and can be used when upgrading to corresponding second-generation runtimes. If you are updating to the App Engine Go 1.12+ runtime, refer to the migration guide to learn about your migration options for legacy bundled services.

Before you begin

You must register your sender emails as authorized senders. For more information, see who can send email.

Sending mail

To send mail from your application:

1. Use the mail.Message type to set the sender, recipient, subject, and body of the message.

2. Send the email with the mail.Send function.

The following example sends an email message to the user as a confirmation that they have created a new account with the application:

import (
	"bytes"
	"fmt"
	"net/http"

	"google.golang.org/appengine"
	"google.golang.org/appengine/log"
	"google.golang.org/appengine/mail"
)

func confirm(w http.ResponseWriter, r *http.Request) {
	ctx := appengine.NewContext(r)
	addr := r.FormValue("email")
	url := createConfirmationURL(r)
	msg := &mail.Message{
		Sender:  "Example.com Support <[e-mail]>",
		To:      []string{addr},
		Subject: "Confirm your registration",
		Body:    fmt.Sprintf(confirmMessage, url),
	}
	if err := mail.Send(ctx, msg); err != nil {
		log.Errorf(ctx, "Couldn't send email: %v", err)
	}
}

const confirmMessage = `
Thank you for creating an account!
Please confirm your email address by clicking on the link below:

%s
`

Receiving mail

You can set up your app to receive incoming email at addresses in the following format:

[e-mail]

Note: Even if your app is deployed on a custom domain, you can't receive email sent to addresses in that domain.

To receive email:

1. Enable incoming mail in your app's app.yaml file:

   inbound_services:
   - mail

2. Set up a handler to process incoming emails, which are supplied to your app as MIME data in an HTTP POST request.

   1. In your app, register a handler to the /_ah/mail/ path:

      func init() {
      	http.HandleFunc("/_ah/mail/", incomingMail)
      }
      

   2. In the handler, read the email's data from the *http.Request:

      func incomingMail(w http.ResponseWriter, r *http.Request) {
      	ctx := appengine.NewContext(r)
      	defer r.Body.Close()
      	var b bytes.Buffer
      	if _, err := b.ReadFrom(r.Body); err != nil {
      		log.Errorf(ctx, "Error reading body: %v", err)
      		return
      	}
      	log.Infof(ctx, "Received mail: %v", b)
      }
      

   You can use the net/mail package in the standard library to parse mail messages.