[Exim] Yet another "failed to open DB file" question

Exim 3.22, GNU/Linux kernel 2.4.6, redhat rpm package on Mandrake 8.1,
amavis-perl (not involved here, I think) on a low loaded PII350 server
(about 400-600 daily deliveries).

I did some research on the last... uhmmm... 2.995 posts and I did not
find anything related to my problem.

The suspect log entry is the same I found on many other posts:

[....] failed to open DB file /var/spool/exim/db/wait-remote_smtp: \
                Permission denied (euid=8 egid=12)

One entry for each remote_smtp delivery. The delivery always complete
succesfully. Removing the /var/spool/exim/db files has no effect: the
next remote_smtp delivery recreate the files as reported (0 byte lenght,
correct uid+guid) but the files seems to be always unaccesible to exim.

Every configuration detail about file access permission looks good:

$ ll /var/spool/exim/db
-rw-r-----    1 mail     mail    0 mar 28 12:30 retry
-rw-r-----    1 mail     mail    0 mar 28 12:30 retry.lockfile
-rw-r-----    1 mail     mail    0 mar 28 12:30 wait-remote_smtp
-rw-r-----    1 mail     mail    0 mar 28 12:30 wait-remote_smtp.lockfile

$ grep exim_[ug] /etc/exim.conf
exim_user = mail
exim_group = mail

$ grep mail /etc/passwd
mail:x:8:12:mail:/var/spool/mail:

The same redhat package whith the same exim.conf was running until 2
weeks ago on redhat 6.2 without any problem.

Any suggestion?

Thanks


Fabio