[Dovecot] Permissions for mail_temp_dir directory

[Henrik Larsson]

I recently upgraded from 2.1.16 to 2.2.2 and started to receive the 
following errors:
imap(hen...@example.com): Error: 
stat(/var/db/dovecot/dovecot.imap.mail.example.com.16128.3209d13f842955c2) 
failed: Permission denied
imap(hen...@example.com): Error: Temp file creation to 
/var/db/dovecot/dovecot.imap.mail.example.com.16128. failed: Permission 
denied
imap(hen...@example.com): Error: 
stat(/var/db/dovecot/dovecot.imap.mail.example.com.16501.0ddff1dc93cdbe6a) 
failed: Permission denied
imap(hen...@example.com): Error: Temp file creation to 
/var/db/dovecot/dovecot.imap.mail.example.com.16501. failed: Permission 
denied

I didn't have these before the upgrade. The current permissions for the 
/var/db/dovecot directory is root:wheel 755.

What would be the correct permissions for the mail_temp_dir directory?

doveconf -n output
--cut--
# 2.2.2: /usr/local/etc/dovecot/dovecot.conf
# OS: FreeBSD 8.3-RELEASE-p3 amd64
auth_mechanisms = plain login digest-md5 cram-md5
first_valid_uid = 125
hostname = mail.example.com
listen = *
log_path = /var/log/dovecot
mail_plugins = zlib
mail_privileged_group = postfix
mail_temp_dir = /var/db/dovecot
managesieve_notify_capability = mailto
managesieve_sieve_capability = fileinto reject envelope 
encoded-character vacation subaddress comparator-i;ascii-numeric 
relational regex imap4flags copy include variables body enotify 
environment mailbox date ihave
namespace {
  inbox = yes
  location =
  prefix =
  separator = .
  type = private
}
namespace {
  hidden = yes
  inbox = no
  list = no
  location =
  prefix = INBOX.
  separator = .
  type = private
}
passdb {
  args = /usr/local/etc/dovecot/dovecot-sql.conf.ext
  driver = sql
}
plugin {
  fts = squat
  fts_squat = partial=4 full=10
  sieve = ~/.dovecot.sieve
  sieve_dir = ~/sieve
}
postmaster_address = postmas...@example.com
protocols = imap pop3 lmtp sieve
service auth-worker {
  user = $default_internal_user
}
service auth {
  unix_listener /home/mail/postfix/private/dovecot-auth {
    group = postfix
    mode = 0660
    user = postfix
  }
}
service lmtp {
  executable = lmtp -L
  unix_listener /home/mail/postfix/private/dovecot-lmtp {
    group = postfix
    mode = 0660
    user = postfix
  }
}
ssl_cert = </etc/ssl/mail.example.com-chained.crt
ssl_key = </etc/ssl/mail.example.com.key
userdb {
  args = /usr/local/etc/dovecot/dovecot-sql.conf.ext
  driver = sql
}
protocol lmtp {
  log_path = /var/log/dovecot-deliver
  mail_plugins = zlib sieve
}
protocol lda {
  mail_plugins = zlib sieve
}
protocol imap {
  mail_plugins = zlib imap_zlib
}
--cut--

Best regards
Henrik Larsson