365 smtp client was not authenticated to send anonymous mail

The classic "not authenticated to send anonymous mail" error!

This error typically occurs when your SMTP client (e.g., an email client or a script) is trying to send an email without authenticating with the SMTP server. Here are a few possible reasons and solutions:

  1. Check your SMTP server settings: Ensure that you have the correct SMTP server settings, including the server address, port number, username, and password. Make sure you're using the correct authentication method (e.g., username/password, OAuth, or plain text).
  2. Enable authentication: If your SMTP server requires authentication, you need to enable it in your email client or script. This usually involves setting the Auth or Authentication property to true or 1.
  3. Use a valid username and password: If you're using a username and password, ensure they're correct and valid. If you're using a generic username like "anonymous" or "guest", try using a valid username and password instead.
  4. Check your email client or script configuration: Verify that your email client or script is configured to use the correct authentication method and credentials. For example, if you're using a script, ensure that it's using the correct SMTP library and settings.
  5. Try using a different SMTP server: If you're using a public SMTP server, try switching to a different one. Some public SMTP servers may have stricter authentication requirements or may not allow anonymous sending.
  6. Check your email client or script logs: If you're using an email client or script, check the logs to see if there are any error messages or warnings related to authentication.

Here's an example of how you might enable authentication in a Python script using the smtplib library:

import smtplib

# Set up the SMTP server
server = smtplib.SMTP('smtp.example.com', 587)

# Enable authentication
server.starttls()
server.login('your_username', 'your_password')

# Send the email
msg = 'Subject: Test email\n\nThis is a test email.'
server.sendmail('[email protected]', '[email protected]', msg)

# Close the connection
server.quit()

Remember to replace your_username and your_password with your actual SMTP credentials.