Xfinity Is Blocking Emails from my Gmail Account

Hello. Xfinity has suddenly started blocking any emails sent from my Gmail address -- including to my own two Comcast email addresses (and to my friend's Comcast email). I am receiving this bounce-back message:

451 4.2.0 Throttled - https://postmaster.comcast.net/smtp-error-codes.php#RL000010

Can you please help me get my Gmail address unblocked? It is a work Gmail address and I regularly send messages to my own personal Comcast email accounts. They should not be considered spam, although they may include one or two links (to webpages and videos). Nothing out of the ordinary though and nothing that should get blacklisted. 

Thank you!