Since I use my own mail server, we suddenly started getting a lot of our email bounced. That's not good (to say the least).
Some of the people I spoke to at Charter didn't have a clue about what the problem was or how to deal with people. It took a day; but now it's fixed.
The Spamhaus web page said to send email to postmaster@charter.net. I did that twice, but never received a response. Of course, since my email to other people was bouncing because of the PBL entry, it's possible that the postmaster was just silently discarding email.