Unable to deliver virus warnings to central email address

[Paul Klos]

I'm running Kolab 2.3.2 on Debian Squeeze.

Today I tried to get virus warnings delivered to the central email address virusalerts at mydomain instead of to individual users. This is actually a distribution list that was created when I first 
installed Kolab (or so I believe, at any rate I didn't create it myself and as far as I can remember it has always been there).

I changed the amavisd configuration file and commented out these lines:
#$warnvirusrecip = 1;   # (defaults to false (undef))
#$warnbannedrecip = 1;  # (defaults to false (undef))

I also uncommented this:

$virus_admin = "virusalert\@$mydomain";

So instead of individual users receiving virus warnings, I expected these messages to go to the virusalerts at mydomain distribution list, of which I am the only member. Instead, I got no warnings 
at all anymore, but these messages in the logs:

/kolab/var/kolab-filter/log/filter.log:
Aug 23 21:46:21 Kolab Filter (pid=6526) [error] [horde] Specify either the UID or a search result!; Code: 331 [pid 6526 on line 181 of "/kolab/lib/php/Horde/Kolab/Server/Object.php"]

/kolab/var/postfix/log/postfix.log
Aug 23 21:46:24 bubba <info> postfix/pipe[6525]: 4A6947344B: to=<virusalert at klos.home>, relay=kolabmailboxfilter, delay=17473, delays=17463/1.6/0/8.3, dsn=4.3.0, status=deferred (temporary 
failure)

So my virus warnings did not get delivered at all anymore.

Next I tried to have the virusmails delivered to me personally (paul at mydomain) instead of the virusalerts distribution lists, and this does work. So somehow resolving the recipient fails in case of 
a distribution list.

I also checked to see if I could send a mail to the distribution list manually, using sendmail. I had no issues sending a mail either from or to virusmails at mydomain.

This has left me very confused. Is this bug somehow, or did I forget to configure something?

Any help is greatly appreciated.

Cheers,

Paul