Is there a way to get a running transaction log from a Dovecot instance to synchronize (and I use that word very, very loosely) multiple instances that don't share a network?
Why I would want to do such a thing: I have a couple way stations along a long, winding road through very hilly country, and at each of these stations, I have a few people (and many, many more at one end of the road). Which people are where varies from hour to hour (but they're all members of a known, larger, group of people with accounts). It would be helpful to get communication (however limited) along this road (and establishing direct communication, either through radio or landline, is not feasible within the budget constraints I have), and it is possible to store a complete copy of the mail spool to a small box at each station (the total mail spool over the period I care about is in the tens of megs).
There are trams shuttling back and forth along this road (stopping at each station), and adding a small box (such as a weatherproofed Raspberry Pi with a wifi dongle) to transport files up and down the road is pretty simple. Doing incremental copies of the mail spool is also simple, keeping track of files that get moved or deleted is a bit harder (but still not that bad), but I have no idea how hard it is to track what messages have been seen, especially for the shared folders (which we use instead of mailing lists).
I realize this is not a "normal" use of Dovecot, but given this, does anyone who knows the software (and how it keeps track of messages) better have suggestions on how to approach the problem?