[Mailman-Users] Problems sending to prodigy.net mail server addresses

[Richard Johnson]

I run a small mailman server for our historical recreation group.  Lately, I've been seeing messages like:

<email at hostname>: host al-ip4-mx-vip1.prodigy.net[144.160.235.143] said:
  550 5.7.1 Connections not accepted from servers without a valid sender
  domain.alph733 Fix reverse DNS for 149.28.67.38 (in reply to MAIL FROM
  command)

The addresses "email at hostname" is actually the failed recipient address.  The two giving problems are at pacbell.net and sbcglobal.net.  I assume their email is handled by prodigy.net.

What seems strange is that MOST of the time messages go through just fine, but ever now-and-then I'll get this failure notice.

The messages are all sent to the mailing list "cortha at cortha.org".  I have the mailing list setup with "host_name" set as "cortha.org", so that the address used in the messages will be "cortha at cortha.org" and replies will go there.  The system which is actually handling the mailing list is officially named "peacock.place", but an MX points there from cortha.org.  The reverse DNS (PTR) record gives the peacock.place name, since that's the official hostname.

If Prodigy is comparing the From: address with the PTR record, then, yes, it will not agree.  This would be crazy, since the PTR can only point to one hostname and is supposed to be the official hostname.  I believe I have my DKIM and DMARC info correct as well.

Personally, I think Prodigy just has a problem with no one else has and it seems to be their own, but I'm wondering if there's some way to work with them?

Any help is greatly appreciated!

/raj