Testing incoming/outgoing emails

I am building a service that will allow communication between emails. What I am trying to do is when I user replies to the email, I want to process the email with Laravel. I plan on using mailgun to handle that, but I am still in local development using Laravel Valet and I am not sure on how to test incoming emails. I used mailtrap.io to capture outgoing emails that fire on specific events, but I am now working on when I user replies to that email using their email client, but mailtrap.io doesn't allow for replies. Any idea on how to work on this part of the project without hosting the app on a live domain and configuring mx records for mailgun?