Later on I read the requirements... This person applied to a position named "Email Backend Engineer" but they actually used a third-party product (postmark + turso) for email backend! They also clearly don't think about email too much - the basic stuff, like plaintext email formatting, viewing, and folders (at least inbox + outbox) are simply missing; while there are optional features, like login screen, admin page and backend framework. And backend database does not even containing a email headers map!
That person might be a great engineer, but I don't think they would be a good fit for that specific position. I'd reject them as well.
(A separate question is that hiring manager's second response... We don't do take-home interviews, but I imagine I'd be stumped by a proposal like that, it seems so irregular in a take-home assignment. Still, I can see how the candidate took that response for an approval... perhaps a next candidate would get an extra sentence perhaps something like "actual problem grading would depend on the code quality, number of features implemented, and how close those are to requirements and job description")
Update: read original job description and not just the except from the blog. That person surely omitted some stuff in their blog! the original title was:
"The project is to build a minimal, terminal-inspired email client"
it gave examples:
"Your implementation should take inspiration from existing terminal email tools like aerc, mutt, or even something like himalaya."
wow! that's 100% no hire, serious inability to read the requirements.