Hey Lewis,

On 21/2/25 07:05, Lewis G Rosenthal wrote:

Hi, all...

It's rare that I get an RDNS failure for one of my server IPs, as I know I have (and have just confirmed again) valid RDNS records in my providers' DNS.

Today, att.net rejected mail from us to one of their subscribers with a 550 5.7.1 error:

  <recipient-address @ att.net>
    host ff-ip4-mx-vip1.prodigy.net [144.160.159.21]
    SMTP error from remote mail server after MAIL FROM:<sender from the 2rosenthals.com domain>:
    550 5.7.1 Connections not accepted from servers without a valid sender domain.flph829 Fix reverse DNS for 50.73.8.217


50.73.8.217 is our Leesburg, VA public IP on Comcast's network (I know; I'm so ashamed...we're in the only four square blocks in downtown Leesburg where Verizon FiOS is *still* not available). The RDNS record is:

secmgr-va.2rosenthals.com

(verified a few minutes ago at MX-Toolbox)

I'm wondering if anyone else is having difficulty today.

Confirmed also that rdns works for your IP from the other side of the planet..

psmedley@ThinkPad-X13-Gen-1:~$ host 50.73.8.217
217.8.73.50.in-addr.arpa domain name pointer secmgr-va.2rosenthals.com.