How do I resolve the Amazon SES email error "SMTP server requires a secure connection"?

Short description

This error occurs because the sending application didn't attempt to authenticate when it connected to the Amazon SES SMTP interface. Usually this error occurs when the SES API call request used AWS Signature Version 2 (SigV2) instead of AWS Signature Version 4 (SigV4).

Important: If you created your SMTP credentials before January 10, 2019, then your SMTP credentials use AWS SigV2. Credentials created after January 10, 2019 use AWS SigV4 by default.

Resolution

To check the creation time of the SMTP user and migrate to AWS SigV4, complete the following steps:

1. Open the AWS Identity and Access Management (IAM) console.
2. In the navigation pane, choose Users, and then choose the SMTP user name.
3. In the Summary page, note the Created date.
4. If your SMTP user was created before January 10, 2019, then do one of the following:
   Create a new SMTP user and replace the older SMTP user from your sending application.
   -or-
   Convert existing AWS credentials to SMTP credentials.
5. Remove the IAM user to delete the older SMTP AWS SigV2 credentials.

Related information

How do I use SMTP to send emails through Amazon SES?