Sending email via Gmail & Python

The answer shows how to send email with gmail API and python. Also updated the answer to send emails with attachment.

Gmail API & OAuth -> no need to save the username and password in the script.

The first time the script opens a browser to authorize the script and will store credentials locally (it will not store username and password). Consequent runs won't need the browser and can send emails straight.

With this method you will not get errors like SMTPException below and there is no need to allow Access for less secure apps:

raise SMTPException("SMTP AUTH extension not supported by server.")  smtplib.SMTPException: SMTP AUTH extension not supported by server.

Here are the steps to send email using gmail API:

(Wizard link here, More info here)

Step 2: Install the Google Client Library

pip install --upgrade google-api-python-client

Step 3: Use the following script to send email(just change the variables in main function)

import httplib2import osimport oauth2clientfrom oauth2client import client, tools, fileimport base64from email.mime.multipart import MIMEMultipartfrom email.mime.text import MIMETextfrom apiclient import errors, discoveryimport mimetypesfrom email.mime.image import MIMEImagefrom email.mime.audio import MIMEAudiofrom email.mime.base import MIMEBaseSCOPES = 'https://www.googleapis.com/auth/gmail.send'CLIENT_SECRET_FILE = 'client_secret.json'APPLICATION_NAME = 'Gmail API Python Send Email'def get_credentials():    home_dir = os.path.expanduser('~')    credential_dir = os.path.join(home_dir, '.credentials')    if not os.path.exists(credential_dir):        os.makedirs(credential_dir)    credential_path = os.path.join(credential_dir,                                   'gmail-python-email-send.json')    store = oauth2client.file.Storage(credential_path)    credentials = store.get()    if not credentials or credentials.invalid:        flow = client.flow_from_clientsecrets(CLIENT_SECRET_FILE, SCOPES)        flow.user_agent = APPLICATION_NAME        credentials = tools.run_flow(flow, store)        print('Storing credentials to ' + credential_path)    return credentialsdef SendMessage(sender, to, subject, msgHtml, msgPlain, attachmentFile=None):    credentials = get_credentials()    http = credentials.authorize(httplib2.Http())    service = discovery.build('gmail', 'v1', http=http)    if attachmentFile:        message1 = createMessageWithAttachment(sender, to, subject, msgHtml, msgPlain, attachmentFile)    else:         message1 = CreateMessageHtml(sender, to, subject, msgHtml, msgPlain)    result = SendMessageInternal(service, "me", message1)    return resultdef SendMessageInternal(service, user_id, message):    try:        message = (service.users().messages().send(userId=user_id, body=message).execute())        print('Message Id: %s' % message['id'])        return message    except errors.HttpError as error:        print('An error occurred: %s' % error)        return "Error"    return "OK"def CreateMessageHtml(sender, to, subject, msgHtml, msgPlain):    msg = MIMEMultipart('alternative')    msg['Subject'] = subject    msg['From'] = sender    msg['To'] = to    msg.attach(MIMEText(msgPlain, 'plain'))    msg.attach(MIMEText(msgHtml, 'html'))    return {'raw': base64.urlsafe_b64encode(msg.as_bytes())}def createMessageWithAttachment(    sender, to, subject, msgHtml, msgPlain, attachmentFile):    """Create a message for an email.    Args:      sender: Email address of the sender.      to: Email address of the receiver.      subject: The subject of the email message.      msgHtml: Html message to be sent      msgPlain: Alternative plain text message for older email clients                attachmentFile: The path to the file to be attached.    Returns:      An object containing a base64url encoded email object.    """    message = MIMEMultipart('mixed')    message['to'] = to    message['from'] = sender    message['subject'] = subject    messageA = MIMEMultipart('alternative')    messageR = MIMEMultipart('related')    messageR.attach(MIMEText(msgHtml, 'html'))    messageA.attach(MIMEText(msgPlain, 'plain'))    messageA.attach(messageR)    message.attach(messageA)    print("create_message_with_attachment: file: %s" % attachmentFile)    content_type, encoding = mimetypes.guess_type(attachmentFile)    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':        fp = open(attachmentFile, 'rb')        msg = MIMEText(fp.read(), _subtype=sub_type)        fp.close()    elif main_type == 'image':        fp = open(attachmentFile, 'rb')        msg = MIMEImage(fp.read(), _subtype=sub_type)        fp.close()    elif main_type == 'audio':        fp = open(attachmentFile, 'rb')        msg = MIMEAudio(fp.read(), _subtype=sub_type)        fp.close()    else:        fp = open(attachmentFile, 'rb')        msg = MIMEBase(main_type, sub_type)        msg.set_payload(fp.read())        fp.close()    filename = os.path.basename(attachmentFile)    msg.add_header('Content-Disposition', 'attachment', filename=filename)    message.attach(msg)    return {'raw': base64.urlsafe_b64encode(message.as_string())}def main():    to = "to@address.com"    sender = "from@address.com"    subject = "subject"    msgHtml = "Hi<br/>Html Email"    msgPlain = "Hi\nPlain Email"    SendMessage(sender, to, subject, msgHtml, msgPlain)    # Send message with attachment:     SendMessage(sender, to, subject, msgHtml, msgPlain, '/path/to/file.pdf')if __name__ == '__main__':    main()

Tip for running this code on linux, with no browser:
If your linux environment has no browser to complete the first time authorization process, you can run the code once on your laptop (mac or windows) and then copy the credentials to the destination linux machine. Credentials are normally stored in the following destination:

~/.credentials/gmail-python-email-send.json

I modified this as follows to work with Python3, inspired by Python Gmail API 'not JSON serializable'

import httplib2import osimport oauth2clientfrom oauth2client import client, toolsimport base64from email.mime.multipart import MIMEMultipartfrom email.mime.text import MIMETextfrom apiclient import errors, discoverySCOPES = 'https://www.googleapis.com/auth/gmail.send'CLIENT_SECRET_FILE = 'client_secret.json'APPLICATION_NAME = 'Gmail API Python Send Email'def get_credentials():    home_dir = os.path.expanduser('~')    credential_dir = os.path.join(home_dir, '.credentials')    if not os.path.exists(credential_dir):        os.makedirs(credential_dir)    credential_path = os.path.join(credential_dir, 'gmail-python-email-send.json')    store = oauth2client.file.Storage(credential_path)    credentials = store.get()    if not credentials or credentials.invalid:        flow = client.flow_from_clientsecrets(CLIENT_SECRET_FILE, SCOPES)        flow.user_agent = APPLICATION_NAME        credentials = tools.run_flow(flow, store)        print('Storing credentials to ' + credential_path)    return credentialsdef SendMessage(sender, to, subject, msgHtml, msgPlain):    credentials = get_credentials()    http = credentials.authorize(httplib2.Http())    service = discovery.build('gmail', 'v1', http=http)    message1 = CreateMessage(sender, to, subject, msgHtml, msgPlain)    SendMessageInternal(service, "me", message1)def SendMessageInternal(service, user_id, message):    try:        message = (service.users().messages().send(userId=user_id, body=message).execute())        print('Message Id: %s' % message['id'])        return message    except errors.HttpError as error:        print('An error occurred: %s' % error)def CreateMessage(sender, to, subject, msgHtml, msgPlain):    msg = MIMEMultipart('alternative')    msg['Subject'] = subject    msg['From'] = sender    msg['To'] = to    msg.attach(MIMEText(msgPlain, 'plain'))    msg.attach(MIMEText(msgHtml, 'html'))    raw = base64.urlsafe_b64encode(msg.as_bytes())    raw = raw.decode()    body = {'raw': raw}    return bodydef main():    to = "to@address.com"    sender = "from@address.com"    subject = "subject"    msgHtml = "Hi<br/>Html Email"    msgPlain = "Hi\nPlain Email"    SendMessage(sender, to, subject, msgHtml, msgPlain)if __name__ == '__main__':    main()

Here is the Python 3.6 code (and explanations) needed to send an email without (or with) an attachment.

(To send with attachment just uncomment the 2 lines bellow ## without attachment and comment the 2 lines bellow ## with attachment)

All the credit (and up-vote) to apadana

import httplib2import osimport oauth2clientfrom oauth2client import client, toolsimport base64from email import encoders#needed for attachmentimport smtplib  import mimetypesfrom email import encodersfrom email.message import Messagefrom email.mime.audio import MIMEAudiofrom email.mime.base import MIMEBasefrom email.mime.image import MIMEImagefrom email.mime.multipart import MIMEMultipartfrom email.mime.text import MIMETextfrom email.mime.application import MIMEApplication#List of all mimetype per extension: http://help.dottoro.com/lapuadlp.php  or http://mime.ritey.com/from apiclient import errors, discovery  #needed for gmail service## About credentials# There are 2 types of "credentials": #     the one created and downloaded from https://console.developers.google.com/apis/ (let's call it the client_id) #     the one that will be created from the downloaded client_id (let's call it credentials, it will be store in C:\Users\user\.credentials)        #Getting the CLIENT_ID             # 1) enable the api you need on https://console.developers.google.com/apis/            # 2) download the .json file (this is the CLIENT_ID)            # 3) save the CLIENT_ID in same folder as your script.py             # 4) update the CLIENT_SECRET_FILE (in the code below) with the CLIENT_ID filename        #Optional        # If you don't change the permission ("scope"):             #the CLIENT_ID could be deleted after creating the credential (after the first run)        # If you need to change the scope:            # you will need the CLIENT_ID each time to create a new credential that contains the new scope.            # Set a new credentials_path for the new credential (because it's another file)def get_credentials():    # If needed create folder for credential    home_dir = os.path.expanduser('~') #>> C:\Users\Me    credential_dir = os.path.join(home_dir, '.credentials') # >>C:\Users\Me\.credentials   (it's a folder)    if not os.path.exists(credential_dir):        os.makedirs(credential_dir)  #create folder if doesnt exist    credential_path = os.path.join(credential_dir, 'cred send mail.json')    #Store the credential    store = oauth2client.file.Storage(credential_path)    credentials = store.get()    if not credentials or credentials.invalid:        CLIENT_SECRET_FILE = 'client_id to send Gmail.json'        APPLICATION_NAME = 'Gmail API Python Send Email'        #The scope URL for read/write access to a user's calendar data          SCOPES = 'https://www.googleapis.com/auth/gmail.send'        # Create a flow object. (it assists with OAuth 2.0 steps to get user authorization + credentials)        flow = client.flow_from_clientsecrets(CLIENT_SECRET_FILE, SCOPES)        flow.user_agent = APPLICATION_NAME        credentials = tools.run_flow(flow, store)    return credentials## Get creds, prepare message and send itdef create_message_and_send(sender, to, subject,  message_text_plain, message_text_html, attached_file):    credentials = get_credentials()    # Create an httplib2.Http object to handle our HTTP requests, and authorize it using credentials.authorize()    http = httplib2.Http()    # http is the authorized httplib2.Http()     http = credentials.authorize(http)        #or: http = credentials.authorize(httplib2.Http())    service = discovery.build('gmail', 'v1', http=http)    ## without attachment    message_without_attachment = create_message_without_attachment(sender, to, subject, message_text_html, message_text_plain)    send_Message_without_attachment(service, "me", message_without_attachment, message_text_plain)    ## with attachment    # message_with_attachment = create_Message_with_attachment(sender, to, subject, message_text_plain, message_text_html, attached_file)    # send_Message_with_attachment(service, "me", message_with_attachment, message_text_plain,attached_file)def create_message_without_attachment (sender, to, subject, message_text_html, message_text_plain):    #Create message container    message = MIMEMultipart('alternative') # needed for both plain & HTML (the MIME type is multipart/alternative)    message['Subject'] = subject    message['From'] = sender    message['To'] = to    #Create the body of the message (a plain-text and an HTML version)    message.attach(MIMEText(message_text_plain, 'plain'))    message.attach(MIMEText(message_text_html, 'html'))    raw_message_no_attachment = base64.urlsafe_b64encode(message.as_bytes())    raw_message_no_attachment = raw_message_no_attachment.decode()    body  = {'raw': raw_message_no_attachment}    return bodydef create_Message_with_attachment(sender, to, subject, message_text_plain, message_text_html, attached_file):    """Create a message for an email.    message_text: The text of the email message.    attached_file: The path to the file to be attached.    Returns:    An object containing a base64url encoded email object.    """    ##An email is composed of 3 part :        #part 1: create the message container using a dictionary { to, from, subject }        #part 2: attach the message_text with .attach() (could be plain and/or html)        #part 3(optional): an attachment added with .attach()     ## Part 1    message = MIMEMultipart() #when alternative: no attach, but only plain_text    message['to'] = to    message['from'] = sender    message['subject'] = subject    ## Part 2   (the message_text)    # The order count: the first (html) will be use for email, the second will be attached (unless you comment it)    message.attach(MIMEText(message_text_html, 'html'))    message.attach(MIMEText(message_text_plain, 'plain'))    ## Part 3 (attachment)     # # to attach a text file you containing "test" you would do:    # # message.attach(MIMEText("test", 'plain'))    #-----About MimeTypes:    # It tells gmail which application it should use to read the attachment (it acts like an extension for windows).    # If you dont provide it, you just wont be able to read the attachment (eg. a text) within gmail. You'll have to download it to read it (windows will know how to read it with it's extension).     #-----3.1 get MimeType of attachment        #option 1: if you want to attach the same file just specify it’s mime types        #option 2: if you want to attach any file use mimetypes.guess_type(attached_file)     my_mimetype, encoding = mimetypes.guess_type(attached_file)    # If the extension is not recognized it will return: (None, None)    # If it's an .mp3, it will return: (audio/mp3, None) (None is for the encoding)    #for unrecognized extension it set my_mimetypes to  'application/octet-stream' (so it won't return None again).     if my_mimetype is None or encoding is not None:        my_mimetype = 'application/octet-stream'     main_type, sub_type = my_mimetype.split('/', 1)# split only at the first '/'    # if my_mimetype is audio/mp3: main_type=audio sub_type=mp3    #-----3.2  creating the attachment        #you don't really "attach" the file but you attach a variable that contains the "binary content" of the file you want to attach        #option 1: use MIMEBase for all my_mimetype (cf below)  - this is the easiest one to understand        #option 2: use the specific MIME (ex for .mp3 = MIMEAudio)   - it's a shorcut version of MIMEBase    #this part is used to tell how the file should be read and stored (r, or rb, etc.)    if main_type == 'text':        print("text")        temp = open(attached_file, 'r')  # 'rb' will send this error: 'bytes' object has no attribute 'encode'        attachment = MIMEText(temp.read(), _subtype=sub_type)        temp.close()    elif main_type == 'image':        print("image")        temp = open(attached_file, 'rb')        attachment = MIMEImage(temp.read(), _subtype=sub_type)        temp.close()    elif main_type == 'audio':        print("audio")        temp = open(attached_file, 'rb')        attachment = MIMEAudio(temp.read(), _subtype=sub_type)        temp.close()                elif main_type == 'application' and sub_type == 'pdf':           temp = open(attached_file, 'rb')        attachment = MIMEApplication(temp.read(), _subtype=sub_type)        temp.close()    else:                                      attachment = MIMEBase(main_type, sub_type)        temp = open(attached_file, 'rb')        attachment.set_payload(temp.read())        temp.close()    #-----3.3 encode the attachment, add a header and attach it to the message    # encoders.encode_base64(attachment)  #not needed (cf. randomfigure comment)    #https://docs.python.org/3/library/email-examples.html    filename = os.path.basename(attached_file)    attachment.add_header('Content-Disposition', 'attachment', filename=filename) # name preview in email    message.attach(attachment)     ## Part 4 encode the message (the message should be in bytes)    message_as_bytes = message.as_bytes() # the message should converted from string to bytes.    message_as_base64 = base64.urlsafe_b64encode(message_as_bytes) #encode in base64 (printable letters coding)    raw = message_as_base64.decode()  # need to JSON serializable (no idea what does it means)    return {'raw': raw} def send_Message_without_attachment(service, user_id, body, message_text_plain):    try:        message_sent = (service.users().messages().send(userId=user_id, body=body).execute())        message_id = message_sent['id']        # print(attached_file)        print (f'Message sent (without attachment) \n\n Message Id: {message_id}\n\n Message:\n\n {message_text_plain}')        # return body    except errors.HttpError as error:        print (f'An error occurred: {error}')def send_Message_with_attachment(service, user_id, message_with_attachment, message_text_plain, attached_file):    """Send an email message.    Args:    service: Authorized Gmail API service instance.    user_id: User's email address. The special value "me" can be used to indicate the authenticated user.    message: Message to be sent.    Returns:    Sent Message.    """    try:        message_sent = (service.users().messages().send(userId=user_id, body=message_with_attachment).execute())        message_id = message_sent['id']        # print(attached_file)        # return message_sent    except errors.HttpError as error:        print (f'An error occurred: {error}')def main():    to = "youremail@gmail.com"    sender = "myemail@gmail.com"    subject = "subject test1"    message_text_html  = r'Hi<br/>Html <b>hello</b>'    message_text_plain = "Hi\nPlain Email"    attached_file = r'C:\Users\Me\Desktop\audio.m4a'    create_message_and_send(sender, to, subject, message_text_plain, message_text_html, attached_file)if __name__ == '__main__':        main()