There a multiple options to test your e-mails locally.
One popular option is Mailtrap.
Working with a staging server online? Not needed. No need to test the last payment step locally? Not needed.
Mollie does communicate via a webhook with the butik application. After creating a payment, mollie will send the answer via webhook.
Define your redirect url in your .env and Mollie does know how to reach your local environment.
Paste your url without
/ at the end.
You can simply share your site via Valet. Past the url into your .env file. That's it. Information about Laravel Valet