Bounce-back email: SMTP not sending or Email Host not Receiving?


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All, emails sent from any domain (all 6 of 6 different people failed) are being bounced back to the sender instead of reaching my 3rd party host Freehostia.

Comcast tier 3 support says they are indeed passing the emails to the 3rd party email host (freehostia) and freehostia says that Comcast isn't sending them through.

I sent Freehostia a bounce-back email message for them to look at and they said that based on the header info it's "obviously" not being passed on from Comcast.

BUT isn't a bounce-back message a message from an SMTP server (comcast) to the original sender? ...and the header wouldn't have any info on the failed routing of the original failed message?

That's my question.

* This problem started Jan. 1st 2017 ...none of my settings have ever changed;

* All emails from everyone else in the world reach me fine;

* Freehostia support (the receiving email host) says "From the headers of the provided bounce it appears that this message is not even leaving comcast system, as you can see:
Reporting-MTA: dns; []
Received-From-MTA: dns; []
Both mail transfer agents are related with their system. Such mail is not even registered in the logs of our mail server."

* The headers of the BOUNCE BACK message is below (not of the actual failed message):

Received: (qmail 123863 invoked by uid 30297); 25 Jan 2017 06:46:18 -0000
Received: from unknown (HELO ([])
(envelope-sender <>)
by (qmail-1.03) with SMTP
for []>; 25 Jan 2017 06:46:18 -0000
Received: from ([])
by with bizsmtp
id cWmH1u00E0mMe4t01WmHBF; Tue, 24 Jan 2017 23:46:18 -0700
Date: Wed, 25 Jan 2017 06:46:17 +0000
To: [deleted]@[deleted].com
Subject: Permanent Error
MIME-Version: 1.0
Content-Type: multipart/report; boundary="------------I305M09060309060P_064914853267770"
X-Nonspam: None

Thanks for answering my question, which is: Does a BOUNCE-BACK email message header (not the actual failed email) contain enough info in it to determine if the email host is rejecting the message, or if the original SMTP sending host isn't passing it on?