moderated Reverse DNS problem #bug

Henning Schulzrinne

I can't quite tell where this is happening, but reverse DNS seems to have difficulties, starting a few days ago:

The original message was received at Tue, 13 Oct 2020 13:58:13 -0400
from []
   ----- The following addresses had permanent fatal errors -----
    (reason: 500 Invalid request, no reverse DNS for
   ----- Transcript of session follows -----
... while talking to
>>> RCPT To:<>
<<< 500 Invalid request, no reverse DNS for
554 5.0.0 Service unavailable
451 4.4.1 reply: read error from
... while talking to
>>> DATA
<<< 500 5.5.1 Invalid command


host domain name pointer

I tried this from multiple vantage points (Verizon, AWS, a large university, and mxtoolbox).

Henning Schulzrinne

Join to automatically receive all group messages.