Send and receive emails to and from comcast customers

For several weeks now we cannot send or receive emails to and from comcast customers.

My provider says comcast changed their filiter system and that is what is causing the problem.

This is the mail system at host hapkido.dreamhost.com.

I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.

If you are a current customer of DreamHost, please contact our
technical support team here

https://panel.dreamhost.com/support

If you are not a customer please use our contact form at.

http://dreamhost.com/contact

If you do so, please include this email in your support ticket. You can
delete your own text from the attached returned message.

DreamHost Email Support

    customer address deleted for obvious reasons>: delivery temporarily suspended: host
    mx1.comcast.net[96.114.157.80] refused to talk to me: 554
    resimta-po-21v.sys.comcast.net resimta-po-21v.sys.comcast.net 66.33.216.122
    Comcast block for spam.  Please see
    http://postmaster.comcast.net/smtp-error-codes.php#BL000000