There are two ways to send email using the Gmail API:
- You can send it directly using the
messages.sendmethod. - You can send it from a draft, using the
drafts.sendmethod.
Emails are sent as base64url encoded strings within the raw
property of a message resource
. The high-level
workflow to send an email is to:
- Create the email content in some convenient way and encode it as a base64url string.
- Create a new message resource and set its
rawproperty to the base64url string you just created. - Call
messages.send, or, if sending a draft,drafts.sendto send the message.
The details of this workflow can vary depending on your choice of client library and programming language.
Creating messages
The Gmail API requires MIME email messages compliant with RFC 2822 and encoded as base64url strings. Many programming languages have libraries or utilities that simplify the process of creating and encoding MIME messages. The following code examples demonstrate how to create a MIME message using the Google APIs client libraries for various languages.
Java
Creating an email message can be greatly simplified with the MimeMessage
class in the javax.mail.internet
package. The following example shows how
to create the email message, including the headers:
gmail/snippets/src/main/java/CreateEmail.java
import java.util.Properties ; import javax.mail.MessagingException ; import javax.mail.Session ; import javax.mail.internet.InternetAddress ; import javax.mail.internet.MimeMessage ; /* Class to demonstrate the use of Gmail Create Email API */ public class CreateEmail { /** * Create a MimeMessage using the parameters provided. * * @param toEmailAddress email address of the receiver * @param fromEmailAddress email address of the sender, the mailbox account * @param subject subject of the email * @param bodyText body text of the email * @return the MimeMessage to be used to send email * @throws MessagingException - if a wrongly formatted address is encountered. */ public static MimeMessage createEmail ( String toEmailAddress , String fromEmailAddress , String subject , String bodyText ) throws MessagingException { Properties props = new Properties (); Session session = Session . getDefaultInstance ( props , null ); MimeMessage email = new MimeMessage ( session ); email . setFrom ( new InternetAddress ( fromEmailAddress )); email . addRecipient ( javax . mail . Message . RecipientType . TO , new InternetAddress ( toEmailAddress )); email . setSubject ( subject ); email . setText ( bodyText ); return email ; } }
The next step is to encode the MimeMessage
, instantiate a Message
object, and set the base64url encoded message string as the value of the raw
property.
gmail/snippets/src/main/java/CreateMessage.java
import com.google.api.services.gmail.model.Message ; import java.io.ByteArrayOutputStream ; import java.io.IOException ; import javax.mail.MessagingException ; import javax.mail.internet.MimeMessage ; import org.apache.commons.codec.binary.Base64 ; /* Class to demonstrate the use of Gmail Create Message API */ public class CreateMessage { /** * Create a message from an email. * * @param emailContent Email to be set to raw of message * @return a message containing a base64url encoded email * @throws IOException - if service account credentials file not found. * @throws MessagingException - if a wrongly formatted address is encountered. */ public static Message createMessageWithEmail ( MimeMessage emailContent ) throws MessagingException , IOException { ByteArrayOutputStream buffer = new ByteArrayOutputStream (); emailContent . writeTo ( buffer ); byte [] bytes = buffer . toByteArray (); String encodedEmail = Base64 . encodeBase64URLSafeString ( bytes ); Message message = new Message (); message . setRaw ( encodedEmail ); return message ; } }
Python
The following code sample demonstrates creating a MIME message, encoding to
a base64url string, and assigning it to the raw
field of the Message
resource:
gmail/snippet/send mail/create_draft.py
import base64 from email.message import EmailMessage import google.auth from googleapiclient.discovery import build from googleapiclient.errors import HttpError def gmail_create_draft (): """Create and insert a draft email. Print the returned draft's message and id. Returns: Draft object, including draft id and message meta data. Load pre-authorized user credentials from the environment. TODO(developer) - See https://developers.google.com/identity for guides on implementing OAuth2 for the application. """ creds , _ = google . auth . default () try : # create gmail api client service = build ( "gmail" , "v1" , credentials = creds ) message = EmailMessage () message . set_content ( "This is automated draft mail" ) message [ "To" ] = "gduser1@workspacesamples.dev" message [ "From" ] = "gduser2@workspacesamples.dev" message [ "Subject" ] = "Automated draft" # encoded message encoded_message = base64 . urlsafe_b64encode ( message . as_bytes ()) . decode () create_message = { "message" : { "raw" : encoded_message }} # pylint: disable=E1101 draft = ( service . users () . drafts () . create ( userId = "me" , body = create_message ) . execute () ) print ( f 'Draft id: { draft [ "id" ] } \n Draft message: { draft [ "message" ] } ' ) except HttpError as error : print ( f "An error occurred: { error } " ) draft = None return draft if __name__ == "__main__" : gmail_create_draft ()
Creating messages with attachments
Creating a message with an attachment is like creating any other message, but the process of uploading the file as a multi-part MIME message depends on the programming language. The following code examples demonstrate possible ways of creating a multi-part MIME message with an attachment.
Java
The following example shows how to create a multi-part MIME message, the encoding and assignment steps are the same as above.
gmail/snippets/src/main/java/CreateDraftWithAttachment.java
import com.google.api.client.googleapis.json.GoogleJsonError ; import com.google.api.client.googleapis.json.GoogleJsonResponseException ; import com.google.api.client.http.HttpRequestInitializer ; import com.google.api.client.http.javanet.NetHttpTransport ; import com.google.api.client.json.gson.GsonFactory ; import com.google.api.services.gmail.Gmail ; import com.google.api.services.gmail.GmailScopes ; import com.google.api.services.gmail.model.Draft ; import com.google.api.services.gmail.model.Message ; import com.google.auth.http.HttpCredentialsAdapter ; import com.google.auth.oauth2.GoogleCredentials ; import java.io.ByteArrayOutputStream ; import java.io.File ; import java.io.IOException ; import java.util.Properties ; import javax.activation.DataHandler ; import javax.activation.DataSource ; import javax.activation.FileDataSource ; import javax.mail.MessagingException ; import javax.mail.Multipart ; import javax.mail.Session ; import javax.mail.internet.InternetAddress ; import javax.mail.internet.MimeBodyPart ; import javax.mail.internet.MimeMessage ; import javax.mail.internet.MimeMultipart ; import org.apache.commons.codec.binary.Base64 ; /* Class to demonstrate the use of Gmail Create Draft with attachment API */ public class CreateDraftWithAttachment { /** * Create a draft email with attachment. * * @param fromEmailAddress - Email address to appear in the from: header. * @param toEmailAddress - Email address of the recipient. * @param file - Path to the file to be attached. * @return the created draft, {@code null} otherwise. * @throws MessagingException - if a wrongly formatted address is encountered. * @throws IOException - if service account credentials file not found. */ public static Draft createDraftMessageWithAttachment ( String fromEmailAddress , String toEmailAddress , File file ) throws MessagingException , IOException { /* Load pre-authorized user credentials from the environment. TODO(developer) - See https://developers.google.com/identity for guides on implementing OAuth2 for your application.*/ GoogleCredentials credentials = GoogleCredentials . getApplicationDefault () . createScoped ( GmailScopes . GMAIL_COMPOSE ); HttpRequestInitializer requestInitializer = new HttpCredentialsAdapter ( credentials ); // Create the gmail API client Gmail service = new Gmail . Builder ( new NetHttpTransport (), GsonFactory . getDefaultInstance (), requestInitializer ) . setApplicationName ( "Gmail samples" ) . build (); // Create the email content String messageSubject = "Test message" ; String bodyText = "lorem ipsum." ; // Encode as MIME message Properties props = new Properties (); Session session = Session . getDefaultInstance ( props , null ); MimeMessage email = new MimeMessage ( session ); email . setFrom ( new InternetAddress ( fromEmailAddress )); email . addRecipient ( javax . mail . Message . RecipientType . TO , new InternetAddress ( toEmailAddress )); email . setSubject ( messageSubject ); MimeBodyPart mimeBodyPart = new MimeBodyPart (); mimeBodyPart . setContent ( bodyText , "text/plain" ); Multipart multipart = new MimeMultipart (); multipart . addBodyPart ( mimeBodyPart ); mimeBodyPart = new MimeBodyPart (); DataSource source = new FileDataSource ( file ); mimeBodyPart . setDataHandler ( new DataHandler ( source )); mimeBodyPart . setFileName ( file . getName ()); multipart . addBodyPart ( mimeBodyPart ); email . setContent ( multipart ); // Encode and wrap the MIME message into a gmail message ByteArrayOutputStream buffer = new ByteArrayOutputStream (); email . writeTo ( buffer ); byte [] rawMessageBytes = buffer . toByteArray (); String encodedEmail = Base64 . encodeBase64URLSafeString ( rawMessageBytes ); Message message = new Message (); message . setRaw ( encodedEmail ); try { // Create the draft message Draft draft = new Draft (); draft . setMessage ( message ); draft = service . users (). drafts (). create ( "me" , draft ). execute (); System . out . println ( "Draft id: " + draft . getId ()); System . out . println ( draft . toPrettyString ()); return draft ; } catch ( GoogleJsonResponseException e ) { // TODO(developer) - handle error appropriately GoogleJsonError error = e . getDetails (); if ( error . getCode () == 403 ) { System . err . println ( "Unable to create draft: " + e . getDetails ()); } else { throw e ; } } return null ; } }
Python
Similar to the previous example, this example also handles encoding the
message to base64url and assigning it to the raw
field of the Message
resource.
gmail/snippet/send mail/create_draft_with_attachment.py
import base64 import mimetypes import os from email.message import EmailMessage from email.mime.audio import MIMEAudio from email.mime.base import MIMEBase from email.mime.image import MIMEImage from email.mime.text import MIMEText import google.auth from googleapiclient.discovery import build from googleapiclient.errors import HttpError def gmail_create_draft_with_attachment (): """Create and insert a draft email with attachment. Print the returned draft's message and id. Returns: Draft object, including draft id and message meta data. Load pre-authorized user credentials from the environment. TODO(developer) - See https://developers.google.com/identity for guides on implementing OAuth2 for the application. """ creds , _ = google . auth . default () try : # create gmail api client service = build ( "gmail" , "v1" , credentials = creds ) mime_message = EmailMessage () # headers mime_message [ "To" ] = "gduser1@workspacesamples.dev" mime_message [ "From" ] = "gduser2@workspacesamples.dev" mime_message [ "Subject" ] = "sample with attachment" # text mime_message . set_content ( "Hi, this is automated mail with attachment.Please do not reply." ) # attachment attachment_filename = "photo.jpg" # guessing the MIME type type_subtype , _ = mimetypes . guess_type ( attachment_filename ) maintype , subtype = type_subtype . split ( "/" ) with open ( attachment_filename , "rb" ) as fp : attachment_data = fp . read () mime_message . add_attachment ( attachment_data , maintype , subtype ) encoded_message = base64 . urlsafe_b64encode ( mime_message . as_bytes ()) . decode () create_draft_request_body = { "message" : { "raw" : encoded_message }} # pylint: disable=E1101 draft = ( service . users () . drafts () . create ( userId = "me" , body = create_draft_request_body ) . execute () ) print ( f 'Draft id: { draft [ "id" ] } \n Draft message: { draft [ "message" ] } ' ) except HttpError as error : print ( f "An error occurred: { error } " ) draft = None return draft def build_file_part ( file ): """Creates a MIME part for a file. Args: file: The path to the file to be attached. Returns: A MIME part that can be attached to a message. """ content_type , encoding = mimetypes . guess_type ( file ) if content_type is None or encoding is not None : content_type = "application/octet-stream" main_type , sub_type = content_type . split ( "/" , 1 ) if main_type == "text" : with open ( file , "rb" ): msg = MIMEText ( "r" , _subtype = sub_type ) elif main_type == "image" : with open ( file , "rb" ): msg = MIMEImage ( "r" , _subtype = sub_type ) elif main_type == "audio" : with open ( file , "rb" ): msg = MIMEAudio ( "r" , _subtype = sub_type ) else : with open ( file , "rb" ): msg = MIMEBase ( main_type , sub_type ) msg . set_payload ( file . read ()) filename = os . path . basename ( file ) msg . add_header ( "Content-Disposition" , "attachment" , filename = filename ) return msg if __name__ == "__main__" : gmail_create_draft_with_attachment ()
Sending messages
Once you have created a message, you can send it by supplying it in the
request body of a call to messages.send
, as demonstrated
in the following examples.
Java
gmail/snippets/src/main/java/SendMessage.java
import com.google.api.client.googleapis.json.GoogleJsonError ; import com.google.api.client.googleapis.json.GoogleJsonResponseException ; import com.google.api.client.http.HttpRequestInitializer ; import com.google.api.client.http.javanet.NetHttpTransport ; import com.google.api.client.json.gson.GsonFactory ; import com.google.api.services.gmail.Gmail ; import com.google.api.services.gmail.GmailScopes ; import com.google.api.services.gmail.model.Message ; import com.google.auth.http.HttpCredentialsAdapter ; import com.google.auth.oauth2.GoogleCredentials ; import java.io.ByteArrayOutputStream ; import java.io.IOException ; import java.util.Properties ; import javax.mail.MessagingException ; import javax.mail.Session ; import javax.mail.internet.InternetAddress ; import javax.mail.internet.MimeMessage ; import org.apache.commons.codec.binary.Base64 ; /* Class to demonstrate the use of Gmail Send Message API */ public class SendMessage { /** * Send an email from the user's mailbox to its recipient. * * @param fromEmailAddress - Email address to appear in the from: header * @param toEmailAddress - Email address of the recipient * @return the sent message, {@code null} otherwise. * @throws MessagingException - if a wrongly formatted address is encountered. * @throws IOException - if service account credentials file not found. */ public static Message sendEmail ( String fromEmailAddress , String toEmailAddress ) throws MessagingException , IOException { /* Load pre-authorized user credentials from the environment. TODO(developer) - See https://developers.google.com/identity for guides on implementing OAuth2 for your application.*/ GoogleCredentials credentials = GoogleCredentials . getApplicationDefault () . createScoped ( GmailScopes . GMAIL_SEND ); HttpRequestInitializer requestInitializer = new HttpCredentialsAdapter ( credentials ); // Create the gmail API client Gmail service = new Gmail . Builder ( new NetHttpTransport (), GsonFactory . getDefaultInstance (), requestInitializer ) . setApplicationName ( "Gmail samples" ) . build (); // Create the email content String messageSubject = "Test message" ; String bodyText = "lorem ipsum." ; // Encode as MIME message Properties props = new Properties (); Session session = Session . getDefaultInstance ( props , null ); MimeMessage email = new MimeMessage ( session ); email . setFrom ( new InternetAddress ( fromEmailAddress )); email . addRecipient ( javax . mail . Message . RecipientType . TO , new InternetAddress ( toEmailAddress )); email . setSubject ( messageSubject ); email . setText ( bodyText ); // Encode and wrap the MIME message into a gmail message ByteArrayOutputStream buffer = new ByteArrayOutputStream (); email . writeTo ( buffer ); byte [] rawMessageBytes = buffer . toByteArray (); String encodedEmail = Base64 . encodeBase64URLSafeString ( rawMessageBytes ); Message message = new Message (); message . setRaw ( encodedEmail ); try { // Create send message message = service . users (). messages (). send ( "me" , message ). execute (); System . out . println ( "Message id: " + message . getId ()); System . out . println ( message . toPrettyString ()); return message ; } catch ( GoogleJsonResponseException e ) { // TODO(developer) - handle error appropriately GoogleJsonError error = e . getDetails (); if ( error . getCode () == 403 ) { System . err . println ( "Unable to send message: " + e . getDetails ()); } else { throw e ; } } return null ; } }
Python
gmail/snippet/send mail/send_message.py
import base64 from email.message import EmailMessage import google.auth from googleapiclient.discovery import build from googleapiclient.errors import HttpError def gmail_send_message (): """Create and send an email message Print the returned message id Returns: Message object, including message id Load pre-authorized user credentials from the environment. TODO(developer) - See https://developers.google.com/identity for guides on implementing OAuth2 for the application. """ creds , _ = google . auth . default () try : service = build ( "gmail" , "v1" , credentials = creds ) message = EmailMessage () message . set_content ( "This is automated draft mail" ) message [ "To" ] = "gduser1@workspacesamples.dev" message [ "From" ] = "gduser2@workspacesamples.dev" message [ "Subject" ] = "Automated draft" # encoded message encoded_message = base64 . urlsafe_b64encode ( message . as_bytes ()) . decode () create_message = { "raw" : encoded_message } # pylint: disable=E1101 send_message = ( service . users () . messages () . send ( userId = "me" , body = create_message ) . execute () ) print ( f 'Message Id: { send_message [ "id" ] } ' ) except HttpError as error : print ( f "An error occurred: { error } " ) send_message = None return send_message if __name__ == "__main__" : gmail_send_message ()
If you're trying to send a reply and want the email to thread, make sure that:
- The
Subjectheaders match - The
ReferencesandIn-Reply-Toheaders follow the RFC 2822 standard.
For information on sending a message from a draft, see Creating Drafts .
