The domain isn't the whole product, but for our target niche, a short, memorable handle is a highly valued status asset. We already have 30+ organic people on our waitlist who reserved their handles. As for the infrastructure, Mailgun is only being used for a working prototype. Using their webhooks was simply the fastest way to validate the core mechanics.
Now that the prototype is working, this is the reason I'm looking for a founding engineer to take over this functional proof-of-concept and help migrate us to a custom, cost-effective, and fully controlled email stack from the ground up.