How would you go about building this?
I want to build an email service where people can send an email to a specific email address. such as example@exampleapp.com.
Then I am able to continuously read new emails, read the info on a server, process the info make API calls then generate an accurate response and send the appropriate response.
Any help with an appropriate stack and technologies would be greatly appreciated.
You can do it all on Amazon AWS, with a bit of work. Amazon SES can handle incoming email to a domain and route it to a SQS queue, or directly to a Lambda (serverless) function. The Lambda code can be a Node.js or Python script that does all the heavy lifting and either send emails out etc.
I believe you can remain within the free tier until you get to some huge volumes (like over 5000 emails per day, or more than a few hours of continuous Lambda running time per day).
You can MVP this very quickly with Zapier (https://zapier.com/apps/email/integrations/webhook).
You can for example set forward rule in your MUA or MTA that handles your email domain and forward mails to Postmark’s inbound email address and it will trigger a webhook you defined.
You can even have a complete subdomain dedicated to inbound emails and setting up a proper MX record postmark can handle every incoming mail: https://postmarkapp.com/developer/user-guide/inbound/inbound-domain-forwarding