Ask Slashdot: How To Unblock Email From My Comcast-Hosted Server?

New submitter hawkbug writes For the past 15 years, I have hosted my own email server at home and it's been pretty painless. I had always used a local Denver ISP on a single static IP. Approximately two years ago, I switched to a faster connection, which now is hosted on Comcast. They provide me 5 static IPs and much faster speeds. It's a business connection with no ports blocked, etc. It has been mostly fine these last two years, with the occasional outage due to typical Comcast issues. About two weeks ago, I came across a serious issue. The following email services started rejecting all email from my server: Hotmail, Yahoo, and Gmail. I checked, and my IP is not on any real time blacklists for spammers, and I don't have any security issues. My mail server is not set as an open relay, and I use SPF records and pass all SPF tests. It appears that all three of those major email services started rejecting email from me based on a single condition: Comcast. I can understand the desire to limit spam — but here is the big problem: I have no way to combat this. With Gmail, I can instruct users to flag my emails as "not spam" because the emails actually go through, but simply end up in the spam folder. Yahoo and Hotmail on the other hand, just flat out reject the traffic at lower level. They send rejection notices back to my server that contain "tips" on how to make sure I'm not an open relay, causing spam, etc. Since I am not doing any of those things, I would expect some sort of option to have my IP whitelisted or verified. However, I can not find a single option to do so. The part that bugs me is that this happened two weeks ago with multiple major email services. Obviously, they are getting anti-spam policies from a central location of some kind. I don't know where. If I did, I could possibly go after the source and try to get my IP whitelisted. When I ask my other tech friends what they would do, they simply suggest changing ISPs. Nobody likes Comcast, but I don't have a choice here. I'm two years into a three-year contract. So, moving is not an option. Is there anything I can do to remedy this situation?