[exim] what is this <nobody@ripn.net>?

Might be a coincidence, but a minute after having sent to two list users:

2004-09-02 16:24:43 I3F6T7-000M0P-BF <= that's me @humph.com
H=213-92-104-121.f5.ngi.it (it.humph.com) [213.92.104.121] P=asmtp
X=TLSv1:RC4-SHA:128 A=plain S=2225
id=a06110409bd5ceaa7bd9e@???
2004-09-02 16:24:51 I3F6T7-000M0P-BF => first recipient
@dicea.unifi.it R=dnslookup T=remote_smtp H=dipolo.dicea.unifi.it
[150.217.9.2]
2004-09-02 16:24:57 I3F6T7-000M0P-BF => the list @exim.org
R=dnslookup T=remote_smtp H=sesame.csx.cam.ac.uk [131.111.8.41]
2004-09-02 16:24:58 I3F6T7-000M0P-BF => second recipient @t-sys.ru
R=dnslookup T=remote_smtp H=relay.t-sys.ru [62.5.214.74]
2004-09-02 16:24:58 I3F6T7-000M0P-BF Completed

I got this:

2004-09-02 16:25:42 H=relay2.ripn.net [194.85.61.38] Warning:
F=<nobody@???> start delay

this is delayed by 130 seconds at the RCPT phase (for my list account
obviously) as it scores for some important DNSBL. It then gives up
and tries again later, perhaps for another mail sent to the list?

Is this a coincidence or some misconceived antispam device? [the
possibilities are clearly more]

Giuliano