Often you need to receive email which then will be available to your Rails application. Usually it’s done with yet another middle-tier, such as IMAP server and IMAP client. Why not cut the middle man? ReceiveD is a simple LMTP (almost RFC2033 compliant) daemon, which can receive e-mail from Postfix and save it directly to the Mongodb document database.

It can be easily extended to support other backends (PostgreSQL, MySQL, Redis, etc.), but it’s your call!