[Mailman-Users] Bounce Processing

[Richard Robbins]

I recently switched my mailman host to a new provider.  One of my users is
now encountering problems that he hasn't had before.  When he sends a
message to a list an error message is generated that is in the following
form:

From: Mail Delivery System <Mailer-Daemon at cloud1.emwd.com>
To: announce-bounces at usml.net
Cc:
Date: Thu, 14 Apr 2016 13:09:24 -0400
Subject: Mail delivery failed: returning message to sender
This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

  [subscriber's email address appeared here and I deleted it]
    host mxa-00149702.gslb.pphosted.com [67.231.156.216]
    SMTP error from remote mail server after end of data:
    550 5.7.0 You are not authorized to use our domain as a sender address.

Action: failed
Final-Recipient: rfc822; [subscriber's email address appeared here and I
deleted it]
Status: 5.0.0
Remote-MTA: dns; mxa-00149702.gslb.pphosted.com
Diagnostic-Code: smtp; 550 5.7.0 You are not authorized to use our domain
as a sender address.

When I asked my host about this I was told that this is an SPF
configuration issue and that the sender needs to adjust relevant DNS
records.

The subscriber spoke to his IT person who said that this appears to him to
be a blacklist issue and that the host needs to make an adjustment.

Meanwhile, mailman has now removed the subscriber from the mailing list and
I had to put him back on, but I assume he will be deleted soon.

I'm not really sure what to do.

Any advice on how to proceed?