But then there was a glitch, the Reply-to section was being populated by my email address and not Postmatic’s unique ID for each follow comment request from users.
This meant when they hit reply, their comment came to me instead of posting on the site. Cure was to place the word, no quotes, “headers” in the WP-SES Reply-to setting and save. My site can now send comments and follow-up comments to users through Postmatic’s and WP-SES collaborative mojo.