One thing to keep in the back of your mind when using AWS SES to send emails with an IAM policy is; it will not work if you create the IAM policy manually in the Console.
You must create the Policy via the the ‘Create My SMTP Credentials’ button in the SMTP settings page in the SES Console.
If you create them manually or even copy and paste the Policy JSON, you’ll get the following error when trying to send an email:
Failed to authenticate password. Error: 535 Authentication Credentials Invalid