Ok, here's one for the idiot file. I just installed dovecot-1.0.4 on my personal system for testing, a system which has to be the simplest dovecot configuration possible. deliver is barking about something with which version 1.0.3 has no problem. I looked over the wiki, googled, and see nothing wrong.
The error:
deliver(jjb): Sep 07 21:39:40 Fatal: Failed to create storage for 'jjb' with mail 'mbox:/HOME_DIRECTORY_USED_BUT_NOT_GIVEN_BY_USERDB/:INBOX=/var/mail/jjb'
In dovecot.conf:
userdb passwd { # [blocking=yes] - By default the lookups are done in the main dovecot-auth # process. This setting causes the lookups to be done in auth worker # processes. Useful with remote NSS lookups that may block. # NOTE: Be sure to use this setting with nss_ldap or users might get # logged in as each others! #args = args = blocking=yes }
and
mail_location = mbox:~/:INBOX=/var/mail/%u
Clues generously accepted, Jack