Email automation for Amazon Orders - MWS API/SP API

Question

I am trying to create a tool for sending automatic follow up ( review request, feedback request) for the Amazon order and I am using Amazon SES for the email service.

I successfully connected marketplaces via login with Amazon and fetched user order, buyer email etc and sending emails to those buyer emails.

SES shows they are delivered on the buyer email but I can't find them inside seller-buyer messages in amazon seller central. After playing around a bit I added my email as a verified sender on my own account then it sends the email and I can also see inside buyer-seller central.

Now the problem is how can I verify my email as a verified email for other sellers who registered on my website via login with Amazon.

Thanks in advance for the help.