How do you receive email on a simple heroku app domain?

Let’s say you have an app on heroku and you have a domain pointed to heroku via CNAME record.

Let’s say the domain resolves properly…

But now you want to use mailchimp or mailerlite to send updates to some of your users.

But you are required to verify your domain by receiving some email from those services

Is there an easy way to do this? All the solutions I read about talk about setting up a google apps account.