1. Google Mail OAuth 2.0
#

Google Mail through SMTP/IMAP requires OAuth 2.0 (OAuth Wikipedia Link) for authentication. This is part of Google’s effort to enhance security by deprecating less secure app access (basic authentication using just a username and password). OAuth 2.0 offers a more secure, token-based system that supports modern features like multi-factor authentication, granular permission scopes, and token expiration for better protection against credential theft. For technical implementation details, see Google’s documentation here : Google IMAP-SMTP Link.

!!! Proxy Configuration: If your server accesses the internet through a proxy, make sure to whitelist the following domains for Google Mail Authentication: oauth2.googleapis.com

Start by navigating to Google APIs & Services: Google APIs & Services Link
!!!Note: Ensure sure the GMAIL API is enabled at Enabled APIs & services. Google API Library Link





Go to the Credentials menu, click on Create Credentials, and select OAuth client ID:



Select the application type: Web application. Provide a unique name. Then, configure the Authorized redirect URI—this is where Google will redirect you after authorization. The Redirect URL must end with ?command=register_google_mail_api.

    http://127.0.0.1:9090/?command=register_google_mail_api

or

    
    https://your.crushftp.domain.com/?command=register_google_mail_api
    

Finally, click the Create button.



After the credentials are created, copy the Client ID and Client Secret.



!!! Note: You can configure the OAuth consent screen by clicking the link above the Authorized JavaScript origins section:
"The domains you enter in the fields below will be automatically added to your OAuth consent screen as authorized domains."
Click the link to open the OAuth consent screen settings, complete the configuration, and authorize your CrushFTP domain.

---

2. SMTP Settings
#

Navigate to Server Admin -> Preferences -> General Settings -> SMTP Settings:



SMTP Server Used for Emailing: Enter the SMTP server address used for sending emails, such as smtp.gmail.com, using the default port 587.

    smtp.gmail.com:587

SMTP Server Username, Password: If the SMTP server address ends with gmail.com, the corresponding Get Refresh Token button will appear. Click that button to proceed.
!!! Note: To obtain the Refresh Token, the CrushFTP WebInterface’s host and port must match the Redirect URL specified in the Google APIs & Services-> Credentials -> OAuth 2.0 Client IDs. In our example, it was: http://127.0.0.1:9090 or https://your.crushftp.domain.com/

Enter the Client ID , Client Secret. Proceed with the authentication and authorization process. !!! Note: Be sure to sign in with the Google Account that has the necessary permissions, as configured in the Google APIs & Services-> Credentials -> OAuth 2.0 Client IDs. This will automatically configure the SMTP Server Username and SMTP Server Password.



If the domain is unverified, a warning message may appear. Click Advanced and choose to proceed:



Click on the Allow button:



From email address: You must also specify the From email address. !!! Imnportant The From address must exactly match the signed-in Google user’s email address (i.e., the account used to obtain the refresh token). Otherwise, SMTP authentication will fail.

Make sure to enable the SSL/TLS flag to ensure a secure connection.

---

3. PopImapTask
#

Select the IMAPS protocol.
See the description: Google IMAP-SMTP Link



Host:

    imap.gmail.com

Port: 993
If the Host contains gmail.com, the corresponding Get Refresh Token button will appear.
Configure the 1. Google Mail OAuth 2.0 Link

!!! Note: To obtain the Refresh Token, the CrushFTP WebInterface’s host and port must match the Redirect URL specified in the Google APIs & Services-> Credentials -> OAuth 2.0 Client IDs. In our example, it was: http://127.0.0.1:9090 or https://your.crushftp.domain.com/

Enter the Client ID , Client Secret. Proceed with the authentication and authorization process. !!! Note: Be sure to sign in with the Google Account that has the necessary permissions, as configured in the Google APIs & Services-> Credentials -> OAuth 2.0 Client IDs. This will automatically configure the PopImapTask's Mail Username and Mail Password.



If the domain is unverified, a warning message may appear. Click Advanced and choose to proceed:



Click on the Allow button:



!!!Note: Since the email address is required after obtaining the refresh token, the Mail Username field must be adjusted.
Enter your email address followed by a tilde (~) at the beginning of the Mail Username field.

Mail Username : <<your email address>>~<<what was before>> 

For more information, see the general POP/IMAP Task description: POP/IMAP Task – CrushFTP Documentation Link