How to resolve “AWS connection is invalid” under the “Sender email address?”

If you see this error message:

Or this one:

You need to verify your Sender Email Address in AWS (by signing in to AWS console).

Once verified, you can generate AWS credentials like Access key and Secret access key and set your subscriber’s region in AWS.
Then connect the AWS account with MailBluster using the following guide: https://app.mailbluster.com/pages/aws-setup-guide.