[tony17112acst]

Here is Freehostia's replies; they respond to everything I asked:

1/25/2017

Thank you for contacting our Technical Support Department.
In this case you can disable the Blacklist Protection for the particular mailbox, but I can see that you've already did that.
So I'm gonna have to ask for a copy of a bounce message that you referred to, so we can further investigate.
Looking forward to your reply.

1/27/17

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; resqmta-ch2-03v.sys.comcast.net [69.252.207.35]
Received-From-MTA: dns; resomta-ch2-08v.sys.comcast.net [69.252.207.104]
Both mail transfer agents are related with their system. Such mail is not even registered in the logs of our mail server.
We seen such bounces before, and the issue is with comcast services, as the messages is not even leaving their system.
Please contact with comcast technicians again, and ask for more information regarding this problem.
If there is anything else we can assist you with do not hesitate to contact us.

1/28/17 (Me)

I talked with Comcast support technicians and after testing, they concluded that Comcast is not handing off the messages to Freehostia AND 50Webs because you lack a valid: DMARK record, SPF record and DKIM record.
Can you help with this please? It is very important that I get email traffic from Comcast customers as they are very large and I assume many of your clients are having the same problem.

1/28/17

The DMARK and SPF records are managed from the client side, which means that if you need to use such records in your DNS zone you simply have to go to your "DNS Records" section (in the control panel > my domains > dns records menu) and create them.
** Keep in mind that those values / records have an effect only for the outgoing mail messages (the messages that you send from your mailboxes with us toward comcast and others, not for incoming mail messages).
In this case the most likely issue is that the Comcast server from which the messages are send is blacklisted and our filters are not allowing the messages, to make sure that is the issue the sender will have to try and send a test message once again and if the message is not delivered to contact us back informing us from which mailbox it was send, so our administrators can check the logs on our servers.

1/28/17 (Me)

I don't understand DMARC yet, but I did get advice that Comcast shouldn't care whether there is DMARK or not because it's normally for the RECEIVING domain, not the sending (Comcast), so that doesn't make sense to me. Comcast shouldn't care whether Freehostia has DMARC if it's sending the email traffic to you.
Anyway, I am a Comcast customer and I can send a test email anytime. I indeed sent a few this morning and a Comcast support technician ALSO sent one or two.

(1) A few test emails sent this morning had the following facts:
FROM FIELD: tony@tonytonini.com
SMTP: sent with comcast.net SMTP)
SENT TO: mail@anthonytonini.com (hosted by Freehostia)

(2) Another test email by me that was sent with Comcast's WEBMAIL:
FROM FIELD: tonytonini@comcast.net
SMTP: sent with comcast.net SMTP
SENT TO: mail@anthonytonini.com

(3) Another email test from a Comcast technician this morning:
FROM FIELD: csatech276@comcast.net
SMTP: sent with comcast.net SMTP
SENT TO: mail@anthonytonini.com

1/28/17

I will escalate the ticket to our administrators, so that they can check the server logs. We will contact you back once we have any updates from the administrators.

1/28/17 (Me)

One other thing: I had an email expert tell me that it could be malfunctioning greylisting. But I don't know if you impliment it or not, but if you do, could you also look into that - it fits the symptoms.

1/28/17

In this case could you please try sending 3 - 4 mail messages (one after another) from your Comcast mailbox to the mailbox on this hosting account, to make sure that it's not a graylisting issue and also to have more recent information in the server logs for the mail messages.

1/28/17 (Me)

OK, I just sent 4 messages in less than 30 seconds with:
FROM FIELD: tony@tonytonini.com
SMTP: sent with comcast.net SMTP
SENT TO: mail@anthonytonini.com (hosted by Freehostia)

1/29/17

After further investigation our administrators do not see any information on the server logs regarding the send mail messages, which means that they did not even reach our servers. In this case the issue is coming from the server from which the messages were send, so please contact the Comcast support for further assistance (to check their logs since the mails have never left from their server and resolve the issue).