Here are some potential causes and troubleshooting steps you can try:

General Configuration Issues:

    Check Email Settings: Double-check that the email settings in Sangfor NGAF are correct, including the SMTP server address, port number, username, password, and authentication method. Ensure they match the specific requirements of your chosen email service.
    Verify Report Recipients: Make sure the email addresses for report subscriptions are valid and entered correctly.
    Enable Email Notifications: Confirm that email notifications are enabled for the specific reports you want to subscribe to.

Specific Email Service Issues:

    Outlook/Gmail:
        Firewall/Antivirus Restrictions: Temporarily disable firewall or antivirus software on the NGAF server to see if they're blocking outgoing email traffic.
        Two-Factor Authentication: Some email services like Gmail require two-factor authentication. Ensure you've configured the appropriate app password for Sangfor NGAF if used.
        Sending Limits: Be aware of potential sending limits on Gmail or Outlook free accounts. Consider using a dedicated email address with higher sending limits for reports.
    Sangfor Built-in Server:
        Server Status: Ensure the Sangfor email server is running and accessible.
        Authentication Settings: Double-check authentication settings specific to the built-in server.

Additional troubleshooting:

    Review Logs: Look for error messages in Sangfor NGAF logs related to email sending attempts. These might provide clues about the specific issue.
    Test Email Functionality: Try sending a test email from Sangfor NGAF manually to a valid recipient outside of report subscriptions. This can help isolate the issue to report subscriptions or email sending in general.
   

Here are some potential causes and troubleshooting steps you can try:

General Configuration Issues:

    Check Email Settings: Double-check that the email settings in Sangfor NGAF are correct, including the SMTP server address, port number, username, password, and authentication method. Ensure they match the specific requirements of your chosen email service.
    Verify Report Recipients: Make sure the email addresses for report subscriptions are valid and entered correctly.
    Enable Email Notifications: Confirm that email notifications are enabled for the specific reports you want to subscribe to.

Specific Email Service Issues:

    Outlook/Gmail:
        Firewall/Antivirus Restrictions: Temporarily disable firewall or antivirus software on the NGAF server to see if they're blocking outgoing email traffic.
        Two-Factor Authentication: Some email services like Gmail require two-factor authentication. Ensure you've configured the appropriate app password for Sangfor NGAF if used.
        Sending Limits: Be aware of potential sending limits on Gmail or Outlook free accounts. Consider using a dedicated email address with higher sending limits for reports.
    Sangfor Built-in Server:
        Server Status: Ensure the Sangfor email server is running and accessible.
        Authentication Settings: Double-check authentication settings specific to the built-in server.

Additional troubleshooting:

    Review Logs: Look for error messages in Sangfor NGAF logs related to email sending attempts. These might provide clues about the specific issue.
    Test Email Functionality: Try sending a test email from Sangfor NGAF manually to a valid recipient outside of report subscriptions. This can help isolate the issue to report subscriptions or email sending in general.