Initial setup - OAuth Follow OAuth 2 Google service to get the Client Id and Client secret . Enable Gmail API in the Google Developer console. Login as admin. Navigate to Site Administrator > Server >  OAuth 2 services Create a new Google service called: Gmail - OAUTH2 . Set the Client id and Client secret . Set the Scopes included in a login request value to: "openid profile email https://mail.google.com " ( Without the quote ). Set the Scopes included in a login request for offline access value to: "openid profile email https://mail.google.com " ( Without the quote ). Save changes. Click Connect to a system account and finish it. Initial setup - SMTP Navigate to Site Administrator > Server > Email > Outgoing Mail Configuration. Set the following value: SMTP hosts: smtp.gmail.com:587 SMTP Security: TLS SMTP Auth Type: XOAUTH2 OAuth 2 Service: Gmail - OAUTH2 SMTP username: The username that was used to connect to Google Developer Console. Save changes Outgoing mail testing Navigate to Site Administrator > Server > Email > Outgoing Mail Configuration -> Test outgoing mail configuration To email address: Your email address to receive the test email. Additional subject: Test email using XOAUTH2 Press Send a test message. Verify that you will see:  This site has successfully sent a test message to the mail server. Open your email inbox. Verify that you will see an email with: Title : [Your site name] : test message. Test email using XOAUTH2 Content : This is a test message to confirm that you have successfully configured your site's outgoing mail. Initial setup - IMAP Navigate to Site Administrator > Server > Email > Incoming Mail Configuration. Set the following value: Enable incoming mail processing: Checked Mailbox name: the name before @ sign of your email address (Ex: Your email is abc@gmail.com, the Mailbox name will be: abc) Email domain: the name after @ sign of your email address. In this case, it will be: gmail.com Incoming Mail Server: imap.gmail.com OAuth 2 Service: Gmail - OAUTH2 Username: The username that was used to connect to the Google Developer Console. Save changes. Navigate to Site Administrator > Server > Email > Message handlers. Enable the Email to Private files. Incoming mail testing Create a new tab on your browser called Tab 1 . On Tab 1, click on the User Profile menu > Profile. Observe the Email address of the admin user. (Example: xyz@gmail.com) Create a new tab on your browser called Tab 2 . On Tab 2 , open the webmail of the Admin's email (Example: https://mail.google.com) On Tab 1 , click on the User Profile menu > Private files. Verify that you will see: You can also e-mail files as attachments straight to your private files space.  Copy the email address. On Tab 2 , compose a new email with the following value: To: The copied email address. Subject: Test attachment Content: Attached Attachment: Attach an image on your machine. Send the email. Run command: php admin/cli/scheduled_task.php --execute='tool_messageinbound\task\pickup_task' On Tab 1, click on the User Profile menu > Private files. Verify that you will see the image that you have sent via email.