make drafts work with Mail
handle other formats than mailto: in list-post and related headers
add timestamp to exception-log to allow collecting multiple logs before investigating
support new (not unread) messages

messages added to the index are marked as new
new state is shown in thread-index-mode and label-list-mode
in thread-index-mode new state can be cleared with refresh (@)
without marking mails as read
list-label-mode sorts labels by latest new message
or if no messages are new, the latest message
TODO: :new label should be made special