I like the idea of a "Progressively Enhanced Monolith". Start by building the core of the application in something like Laravel that can do anything and be developed quickly, then stick it behind a proxy/CDN like Cloudflare. Then if you find endpoints or pages that are accessed frequently and would be better as their own microservice then use a small serverless worker to either respond directly from the edge or forward the request onto a microservice.
I'm jumping on the conversation , actually my portfolio website is on cloudflare pages with astrojs , it costs me nothing to host it , has a quick way to develop . I higly recomend it
Most places and projects I've worked in the past 10 years or so have used GSuite or similar for inboxes, and Amazon SES or similar for programatically sending email. Those that didn't (shared-hosted websites on CPanel installations seemingly do still exist in 2018) had access to webmail in the hosting panel or as an installable application.
Yeah right now I use email forwarding and SES to send emails (which required setting up an address that belongs to my domain, such as user@exampledomain.com).
In this case I forwarded that email to my gmail account and it all works, but it's not perfect.
In either case, having at least email forwarding or an inbox is essential for a lot of common things you'd want to do on a domain. Forwarding works ok to avoid $60 / year for Google's offerings but has some limitations.
This is coming at it from the POV of just setting up a VPS to host some sites and wanting to accept email from your domain name without paying any more than what the domain cost to register.
I think this use case is super common, especially on HN.
No one thought Let's Encrypt would step up and offer a top tier free SSL solution. If it can be done for SSL, it can be done for real inboxes. :)