postfix + spamassassin + mks32 empty mail when mailgroup has morethan 6 members

Hi

I think I have problem with postfix, but i'm not sure. When the
mailgroup has more than 6 members, one of members get empty mail, "one"
is very random, the rest of group get normal mails. The header of the
mail is I don't know where i schould looking for the problem

some configs and logs:

almost empty header:
X-Spam-Checker-Version: SpamAssassin 3.1.7 (2006-10-05) on www.domena.pl
X-Spam-Level: ****
X-Spam-Status: No, score=4.3 required=8.5
tests=EMPTY_MESSAGE,MISSING_SUBJECT,
NO_RECEIVED,NO_RELAYS,TO_CC_NONE autolearn=no version=3.1.7
firma-X-MKS-Scan: <www> Mon, 17 Sep 2007 14:59:06 +0200

postfix virtual:
service@domain.com andy, art, kal, ag, such, pit, ewe

file local.cf

trusted_networks [ip]
whitelist_from @domena.pl
allow_user_rules 1
required_score 8.5
score RCVD_IN_BL_SPAMCOP_NET 3
score RCVD_IN_SORBS_DUL 3
use_bayes 1
bayes_auto_learn 1
auto_whitelist_path /var/spool/spamassassin/auto_whitelist
bayes_path /var/spool/spamassassin/bayes

postfix's log:
Sep 17 17:40:53 www spamd[28048]: spamd: clean message (4.3/8.5) for
root:1231 in 13.4 seconds, 99 bytes.

Sep 17 17:40:53 www spamd[28048]: spamd: result: . 4 -
EMPTY_MESSAGE,MISSING_SUBJECT,NO_RECEIVED,NO_RELAY S,TO_CC_NONE
scantime=13.4,size=99,user=root,uid=1231,required_ score=8.5,rhost=localhost,raddr=127.0.0.1,rport=54 437,mid=(unknown),autolearn=no

Sep 17 17:40:53 www postfix/local[29932]: B3CAFA4EB8:
to=<aga@mail.domena.pl>, orig_to=<serwis@domena.pl>, relay=local, delay=85,
status=sent (delivered to command: /usr/bin/procmail)

thx for some clue

pawel