Updated TODO list. Added:

* rework locking
 * IMAP SEARCH BEFORE matching dates only, no time
 * document mbox format issues

TODO

@@ -1,3 +1,32 @@
+LOCKING & Co:
+* switch to or add fcntl() locking; when combining with flock, be careful not to
+  break on Solaris/FreeBSD, where flock() is just fcntl() so using both would
+  block. 
+* Ensure that we don't accidently lose fcntl locks when closing some file
+  descriptor; this applies even for flock, since again, it might be emulated
+  with fcntl
+* Block signals while writing changed mailbox back. Also, we probably shouldn't
+  use shutil.copy2() for this; at least we have to handle symlinked targets in a
+  sane way, see Debian bug #349068.  mbox_sync_mailbox() in the mutt code might
+  be an example how to write back a changed mailbox. 
+* Double-check the entire locking code. 
+
+IMAP SEARCH BEFORE disregards time and timezone information.  This should at
+least be documented.  E.g. I've found that '-d 0' didn't match all messages in
+an IMAP mailbox.  This is because the SEARCH key is (BEFORE 14-Nov-2007) on 14
+November, not matching messages that arrived today.  Do we need an '--all'
+option to fix this? 
+
+Document mbox format issues: link to
+http://homepages.tesco.net/~J.deBoynePollard/FGA/mail-mbox-formats.html, 
+qmail mbox manpage, Debian manpage, RFC 4155.  Document what mbox format we can
+read, and what we write. 
+FIXME: we cannot yet parse rfc 2822 addr-spec stuff like quoted local-parts in
+return-path addresses.
+
+Minor annoyance: when a From_ line is generated, guess_delivery_time() reports
+the used date header a second time. 
+
 Check sf.net and Debian BTS for new bugs.  Again.
 
 IMAP: ensure mailbox archives are properly named.  Currently imap folder names