Hackweek 21?

Postmaster desperately needs a mail spool. I need to come up with a good way to store meta information about queued messages. An sqlite database seems like a natural fit because I might want to do some nontrivial queries in there to figure out which messages to deliver (and where). On the other hand, interfacing with sqlite is a bit unpleasant, so instead I might want to write one big JSON file that contains all relevant information. That would certainly suffice for the first version ...