unknown rDNS

"Thomas Barth via users" <[email protected]> Sat, 08 Nov 2025 14:35:55 +0100
Newsgroups gmane.mail.spam.spamassassin.general
Message-ID <[email protected]>
Hi,
I’m trying to understand why the first unthrusted mail hop in a received 
header shows rDNS: unknown, but when I check the same IP manually using 
dig -x, I do get a PTR record.

Received: from suomenporakaivo.fi (unknown [107.150.1.216])

Why would SpamAssassin / Postfix log unknown in this case? Could it be 
due to a temporary DNS lookup failure, caching issue, or something else? 
Only two hours have passed since the spam was received.

Best regards,
Thomas B