[exim] Spool file not found

Hi,

I keep seeing the following line in /var/log/exim4/mainlog once or twice
per day:

2007-05-30 07:18:27 1HrrEH-00028W-4K Spool file 1HrrEH-00028W-4K-D not
found

When I run mailq, I get entries with no size entry similar to:

11h       1HrrEH-00028W-4K    <test@???>
          amillar@???

The complete transaction for a single email (from mainlog) is as
follows:

2007-05-29 20:32:25 1Ht7Qe-0006jz-VS <= test@??? H=example.com
[192.168.0.1] P=esmtp S=4972 id=$MSGID$
2007-05-29 20:32:34 1Ht7Qe-0006jz-VS => amillar@???
R=hubbed_hosts T=remote_smtp H=192.168.0.2 [192.168.0.2]
2007-05-29 20:32:34 1Ht7Qe-0006jz-VS Completed
2007-05-29 20:32:35 1Ht7Qe-0006jz-VS Spool file 1Ht7Qe-0006jz-VS-D not
found

The messages are delivered, so this is not a massive problem; however
these emails fill up the output of mailq and are generally annoying.

Is there anything that can be done to fix this?

Thanks,

- Andy