* unless run wit -D a once existent folder will allways be
  recreated because mailsync remembers it in it's .minfo store.
  How to reproduce:
  * create folder F
  * store some file there
  * sync
  * remove F on both sites
  * sync
  * F will be recreated on one site :-/

* Better error handling (if there's an IMAP error mailsync just
  quits)

* integrate current_context_passwd better with c-client calls

* refuse to run if .mailsync contains password and permissions are wrong

* test and/or find better solution to the problem when encountering a mailbox
  that does not match our default mailbox delimiter

* in mailsync.c::copy_message mail_append_full returns an int. c-client's
  mail_append_full return's a long. What exactly is being returned? Go over it
  and maybe replace "rv" by "success".

* mailsync can't handle mailboxes that contain messages _and_ submailboxes

* why do some errors go to stderr and some to stdout?

* ideally sanitize_message_id should not have a side effect, but just
  return 1 or 0 if the message had to be modified or it should have
  enough information to print a sufficient error message, i.e. the
  mailbox where the message is originating from

* I'm not sure whether extra mailboxes in read_lasttime_seen and delete_boxes
  in write_lasttime is consistent

* make naming of read_lasttime_seen and of write_lasttime consistent

* it'd be nice which driver c-client will use for accessing mail

* simulate option would be nice