MX Records Needed to Receive Email at comcast.net email address

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Why is it impossible to find the MX records needed to set up emails to arrive in a comcast.net email address from a custom domain?

In Windows a standard lookup seems to work:

C>nslookup -type=MX comcast.net 75.75.75.75
Server:  cdns01.comcast.net
Address:  75.75.75.75

Non-authoritative answer:
comcast.net     MX preference = 5, mail exchanger = mx1a1.comcast.net
comcast.net     MX preference = 50, mail exchanger = mx1.mxge.comcast.net
comcast.net     MX preference = 50, mail exchanger = mx2.mxge.comcast.net
comcast.net     MX preference = 5, mail exchanger = mx2c1.comcast.net
comcast.net     MX preference = 5, mail exchanger = mx2h1.comcast.net
comcast.net     MX preference = 5, mail exchanger = mx1h1.comcast.net
comcast.net     MX preference = 5, mail exchanger = mx1c1.comcast.net
comcast.net     MX preference = 5, mail exchanger = mx2a1.comcast.net

mx1c1.comcast.net       internet address = 96.102.18.148
mx2a1.comcast.net       internet address = 96.103.145.164
mx2a1.comcast.net       AAAA IPv6 address = 2001:558:fd01:2bad::4
mx1a1.comcast.net       internet address = 96.103.145.165
mx1.mxge.comcast.net    AAAA IPv6 address = 2001:558:fd02:243f::2
mx2c1.comcast.net       AAAA IPv6 address = 2001:558:fd00:4f::5
mx2h1.comcast.net       internet address = 96.102.157.179
mx2h1.comcast.net       AAAA IPv6 address = 2001:558:fd02:243f::3
mx1h1.comcast.net       internet address = 96.102.157.178

Or are you looking for something else?

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My last one got auto-bot flagged, so I'll ask the question a different way. 

You bought a domain name, and you want to use comcast as a primary MX??  Or did I not understand the question?  Cause that isn't going to work.

Yes, that is correct. There is some background as to why I had to transfer the domain to a new host. But, basically that is it. Unfortunately, the new domain host doesn't offer free email forwarding and apparently comcast doesn't allow mx records that aim at their emails so I am stuck paying for the email package from the registrar which is going to just make things more difficult for 60 days until I can change my registrar again.

Welp.  Yep.  The reason why your mail is failing is because comcast does not own your domain, nor do their mail servers know anything about your domain.

If they did accept mail for random domains, they would be an open-relay, and everyone on the planet would block ALL comcast email due to a massive spam flood they would create.

Will it work?  No.  Nor should it.

A lot of hosting companies offer email.  Sometimes for a fee.  Sometimes it's included if you register the name with them.  If you aren't going to run your own mail server, you'll have to shop around.  Xfinity blocks port 25 so running one on a residential account won't work.  You could possibly do that if you pay a service to port redirect email for you and run a mail server on another port.  That's going to make spam control much harder though.  Better, would be lease a VM at a hosting company and run your email server there, or get an Xfinity business account and you won't have the port 25 block for your mail server.

In any case, it's either the register's email server, or are running one yourself somewhere, somehow.