Comcast: Is it the censor to the world of the web?

Comcast keeps blockingt my emails to my sister, my friends and my house manager, all of whom have Comcast accts. Comcast claims I am sending spam. When I (in the past) go in to challenge this using directions supplied by comcast as it returns my email, the reply always is that there is no spam coming from my URL. Yet the conmpany continues to block my emails. It's gotten bad enough I asked my sister and my manager to get accounts outside of Comcast so I could communicate with them. Checking with my ISP (in New Zealand) I learned that several of their users had also --falsely-as it turns out been accused of sending spam. But they couldn't fix the prioblem --only Comcast could. Today I read in the NYTimes that Frank Eliason is the go-to person who can fix this. It's been months my trying and I wish Comcast would stop interfering with my first amendment rights--and my right as a brother to email my sister--or friends for that matter! Currently I am still frustrated.