I want to send an email using Amazon Simple Email Service (SES). However, I receive the error, "SMTP server requires a secure connection or the client is not authenticated. The server response was: Authentication required".
This error indicates that the sending application didn't attempt to authenticate when it connected to the Amazon SES SMTP interface. Usually this error is seen if the SES API call request was signed using AWS Signature version 2 (SigV2), instead of AWS Signature version 4 (SigV4).
Note: If you created your SMTP credentials before January 10, 2019, your SMTP credentials were created using an older version of AWS SigV2. Credentials created after that date use AWS SigV4 by default.
Check the creation time of the SMTP user by following these steps:
- Sign in to the AWS Management Console, and then open the AWS Identity and Access Management (IAM) console.
- In the navigation pane, choose Users, and then choose the SMTP user name.
- A new page loads. You can find "creation time" under summary.
If your SMTP user was created before January 10, 2019, then you receive an error because requests are signed using AWS SigV2.
To resolve the issue, create a new SMTP user from the SES console, and then replace the older SMTP user from your sending application. You can also derive the AWS Sigv4 SMTP username and password from IAM user by converting existing AWS credentials.
If the issue persists, or if your SMTP user was created after January 10, 2019, then open a case with SES support to investigate further.