sendmail sending duplicate messages

[furejuvo]

Hello,

I am having problems with sendmail sending the same message with the same message-ID and same process-ID:
Sep 15 11:16:01

http://www14

sendmail[7752]: m8F97Ke8005718:
to=<@yahoo.co.uk>,<@yahoo.co.uk>,<@yahoo.co.uk>,<@yahoo.co.uk>,<@yahoo.co.uk>,<@yahoo.co.uk>, delay=00:08:38, xdelay=00:00:03, mailer=esmtp, pri=7168047, relay=mx1.mail.ukl.yahoo.com. [195.50.106.7], dsn=2.0.0, stat=Sent (ok dirdel 6/0)

Sep 15 11:16:06

http://www14

sendmail[11289]: m8F97Ke8005718:
to=<@yahoo.co.uk>,<@yahoo.co.uk>,<@yahoo.co.uk>,<@yahoo.co.uk>,<@yahoo.co.uk>,<@yahoo.co.uk>, delay=00:08:43, xdelay=00:00:01, mailer=esmtp, pri=7258047, relay=mx1.mail.ukl.yahoo.com. [195.50.106.7], dsn=2.0.0, stat=Sent (ok dirdel 6/0)

Messages are coming from mailman, the local mailer is procmail, line from sendmail.cf:
Mlocal, P=/usr/bin/procmail, F=lsDFMAw5:/|@qSPfhn9, S=EnvFromL/HdrFromL, R=EnvToL/HdrToL,
A=procmail -t -Y -a $h -d $u

My idea is that as messages get grouped by sendmail, if delivery of one or more of the group fails, sendmail is not deleting the addresses which were sent successfully from that group. Thus they are resent as soon as another attempt to send the message from the queue to the xx addresses.

What causes this and what is the solution?

Thanks,

Tsjebbe
Antenna Foundation