Also, confirm that IPv6 is off, seems more and more places insisting on
RCrDNS on IPv6, and not always doing it right with multiple PTR records..
On 2026-06-17 09:52, Paul Smith via mailop wrote:
We've just started getting lots of errors from attempts to send mail to
Yahoo.com email addresses.
-------------------
<[email protected]>: host mta7.am0.yahoodns.net[67.195.228.110]
said: 550 5.7.25 Forward-confirmed reverse DNS failed tnmpmscs (in reply to
MAIL FROM command)
Reporting-MTA: dns; mx13.vpop3mail.com
X-Postfix-Queue-ID: 1FBE32770F
X-Postfix-Sender: rfc822; [email protected]
Arrival-Date: Wed, 17 Jun 2026 15:08:00 +0000 (UTC)
Final-Recipient: rfc822; [email protected]
Original-Recipient: rfc822;[email protected]
Action: failed Status: 5.7.25 Remote-MTA: dns; mta7.am0.yahoodns.net
Diagnostic-Code: smtp; 550 5.7.25 Forward-confirmed reverse DNS failed
tnmpmscs
-------------------
The messages are being sent from mx13.vpop3mail.com, which is Postfix.
The Postfix 'myhostname' is set to "mx13.vpop3mail.com", the IP address
of mx13.vpop3mail.com
is 178.159.10.132, and the reverse DNS of 178.159.10.132 is
"mx13.vpop3mail.com"
No one else seems to be reporting any FCrDNS errors from that server,
and the errors only just started today, with no configuration changes at
our end.
The 'tnmpmscs' in the error message looks odd - it doesn't mean anything
to me, but it's in all the error responses
Anyone else having similar problems sending to Yahoo?
Paul
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