If you have been bitten by bug #334180 and dovecot 1.0alpha3-2.0.1 rest assured the problem is being worked on. In the meantime you should downgrade to -2 which can be found at:

http://snapshot.debian.net/archive/2005/10/08/debian/pool/main/d/dovecot/

-- Jaldhar H. Vyas jaldhar@debian.org La Salle Debain - http://www.braincells.com/debian/