[exim] Callout lockfile not writable

Hi,

we have an Exim server configured to forward emails to another
mail system (as a spam filtering system with Maia Mailguard (Amavis
and Spamassassin)).

We have a pretty standard Debian configuration setup for Exim,
with the following alterations (These are most of the alterations
we have):

router/01_amavis:

callout:
        debug_print = "Initiating recipient callout to my mail host..."
        driver = manualroute
        verify_only
        transport = recipient_callout
        route_list = * mail.mailgateway.no byname
        host_find_failed = defer

amavis:
        driver = manualroute
        # Don't run (condition=0) if received from port 10025
        # as message has already passed through amavis
        condition = "${if eq {$interface_port}{10025} {0}{1}}"
        transport = amavis
        route_list = "* localhost byname"
        self = send
        no_more

[EOF]

acl/30_exim4-config_check_rcpt:

[... lots of config ... ]

  accept
    domains = +relay_to_domains
    endpass
    message = unknown user
    verify = recipient/callout=10s

# At this point, the address has passed all the checks that have been
# configured, so we accept it unconditionally.

accept

[EOF]

In the Exim mainlog we can see these:

2009-08-06 11:08:23 Failed to get write lock for
/var/spool/exim4/db/callout.lockfile: timed out

On a regular basis, sometimes 10-15 seconds apart.

And lsof reveals this:

quicksilver:/var/spool# lsof|grep lockfile
exim4 6659 Debian-exim 5uW REG 8,1 0 180348
/var/spool/exim4/db/callout.lockfile
exim4 7018 Debian-exim 4u REG 8,1 0 180348
/var/spool/exim4/db/callout.lockfile
exim4 7019 Debian-exim 4u REG 8,1 0 180348
/var/spool/exim4/db/callout.lockfile

When we ran lsof earlier, a lot more processes were also "attached" to
the lockfile,
but only one has the W (write lock for the entire file).

This is a testing environment with very few emails going through
(although spammers
have already managed to figure out it deals with mail..)

Any ideas?

TIA,

Morten

--
Morten W. Petersen
Manager
Nidelven IT Ltd

Phone: +47 45 44 00 69
Email: morten@???