I agree that "inspiration" can be subjective, but in this particular case the solution was so much off that it'd be hard to argue otherwise. There is nothing terminal-like in it, and the tool is not usable as an email client either. Instead of doing login screens and user management, author should have made a page to view individual email or added folder (just 3, inbox/sent/trash, would already be a great improvement)
And if you want to ignore the requirements and work off position description... the position is titled "Email Backend Engineer", and the candidate's solution offloads actual email operations (storage, transfer) to third-party services. I suspect that even if candidate provided the same UX, but would have backed it with SMTP, IMAP, TCP/IP (not via http library), DNS MX lookup, resilient storage etc... then they might have passed.
But author failed to do either serious front-end work (required by question) or serious back-end work (required by job posting), so result was entirely predictable.