[Dovecot] dovecot sendmail mysql no inbox error

[jan gestre]

hi guys,

we are experiencing this particular problem with one of the webmail server
we manage. the server is using dovecot as pop3 and imap server while
sendmail is being used as mta. when this user tries to login via telnet,
this is what i've got:

$ telnet localhost pop3

Trying 127.0.0.1...
Connected to localhost.localdomain (127.0.0.1).
Escape character is '^]'.
+OK dovecot ready.
user user1
+OK
pass password
+OK Logged in.
-ERR No INBOX for user.
Connection closed by foreign host.

when i looked at the maillog i saw this:

Apr 25 20:52:32 samplemail pop3(samplemail): File isn't in mbox format:
/var/mail/samplemail
Apr 25 20:52:32 samplemail pop3(samplemail): File isn't in mbox format:
/var/mail/samplemail
Apr 25 20:52:32 samplemail pop3(samplemail): Couldn't open INBOX: Internal
error occured. Refer to server log for more information. [2007-04-25
20:52:32]

tried google but not much of help, they just suggested to update or replace
dovecot. i already update dovecot and made some changes to default_mail_env
parameter, still the same result.

dovecot version is 0.99 on a fedora 4 box

any idea?