Milter-greylist

Hi,

since a few days I see the following error always produced by the same
sending server (my be domino) and sender every 20 minutes. It's always the
same mail:

Aug 19 12:22:17 server milter-greylist: p7JAME8U015316: addr 88.79.xx.xx
from <sender@...> rcpt <recip@...>: autowhitelisted for
another 768:00:00
Aug 19 14:51:45 server sm-mta[15316]: p7JAME8U015316:
from=<sender@...>, size=125990, class=0, nrcpts=1,
msgid=<@OF45480D59.66ADE979-ONC12578F1.00339A09-C12578F8.00294A3Adomain.de>,
proto=ESMTP, daemon=MTA-v4, relay=domino.domain.de [88.79.xx.xx]
Aug 19 14:51:45 server sm-mta[15316]: p7JAME8U015316: Milter (greylist):
write(L) returned -1, expected 50: Broken pipe
Aug 19 14:51:45 server sm-mta[15316]: p7JAME8U015316: Milter (greylist):
to error state
Aug 19 14:51:45 server sm-mta[15316]: p7JAME8U015316: Milter (mimedefang):
write(L) returned -1, expected 50: Broken pipe
Aug 19 14:51:45 server sm-mta[15316]: p7JAME8U015316: Milter (mimedefang):
to error state
Aug 19 14:51:45 server sm-mta[15316]: p7JAME8U015316: Milter: data,
reject=451 4.3.2 Please try again later
Aug 19 14:51:45 server sm-mta[15316]: p7JAME8U015316:
to=<recip@...>, delay=02:29:28, pri=155990, stat=Please try again
later

I put the sending server to the list "my friends" addr but without any
success. 

Running milter-greylist 4.3.5-3 on debian/lenny.

sendmail.mc:
INPUT_MAIL_FILTER(`greylist',`S=local:/var/run/milter-greylist/milter-greylist.sock,
F=, T=S:1m;R:1m')dnl

I thought F= will let the mail through if the milter fails.

Any ideas?

Thanks
Marcus