Known bugs:
-----------
- the "color parents gray" algorithm has a bug: siblings are
  colored too, sometimes.
- on folder change (rename, move, delete etc.) recalculate
  folder context popup. otherwise there are inconsistencies
  e.g. in the io filter window.
- if you move all mails away from a folder, its statistic is
  not updated correctly in the folder treeview

This is my actual TODO list:
----------------------------
- empty trash
- mark a selection of mails as read
- edit configuration parameters
- input filter: delete operation
- pop3 error window
- smtp error window
- when selecting last selected message in a folder, don't
  set status on read
- prevent opening several instance of the same window, if
  this makes no sense (e.g. account window)
- address book
- date with timezone? +0200
- attachment file selecter:
  - memorize selected folder per session
  - add a button to change to the default directory
- compose close: ask, if mail should be moved to Drafts
- make browser application configurable
- check RFC:
  - which Charset should be used when replying mail?
