My E-mails sent to my Comcast account are being Throttled

I use a redirection service to forward my email to my @comcast.net e-mail.

 

My redirection service often gets a bounce back message.

 

Here is an example of the error received:

 

Nov 15 11:06:44 ns2 sm-mta[24220]: 4AFI6d1s024218: to=<xx@yyy.com>, delay=00:00:05, xdelay=00:00:04, mailer=esmtp, pri=53723, relay=mx1h1.comcast.net. [Edited: "Personal Information"]
], dsn=4.0.0, stat=Deferred: [Edited: "Personal Information"]Throttled - try again later. Please see https://postmaster.comcast.net/smtp-error-codes.php#RL000003

 

I had this problem 4 years ago, and it seemed to have been resolved.

 

I have tried to get it fixed again, but the CSA team at Comcast has been unable to help me with this problem.  On two occasions, I even reached level 3, but they said there was no problem on their end, even though the bounce message above was clearly generated by Comcast.

 

I need whoever administers Comcast's servers to help with this.  It is causing a huge issue.  My incoming email often is delivered late, or not at all.