[spb]

Would it be possible to write something like an SMTP server that feeds directly into Inbox, no Dovecot/Cyrus/IMAP/POP3 required?

[kbenson]

It might be simpler to just use a regular SMTP server and procmail or equivalent to deliver to Inbox, with fallback to local mailbox on failure to deliver, which Inbox could then sync. No need to reinvent the wheel here.

[grinich]

Conceivably, yes. (Though I haven't tried it.)