Importing mbox archives into a inbox?

Greetings from a dovecot newbie. I have a bunch of mailing list archives (in mbox) format that I want to dump into the inbox for a particular account on the system. I want them to retain all of their information, particularly the date. I'm not seeing how to do this, but I could be missing it. Is this LDA or LMTP with some command-line options I'm not seeing?

--Paul Hoffman