In one of my other posts, I lamented that some of our outbound mail from customers was being sent by some people who put non-resolveable domains as the envelope sender. As a result, an ISP (among others) was throttling our mail because the sender's domain had no A-record.
Stuff like this is difficult to take action on. On the one hand, we could work with the ISP to get an understanding like the following: "Look, this one of your customers who is using us as their work account to forward to their home account. Stop throttling us... and them." We could call them up, explain the situation, work out a deal and the problem goes away.
But then it comes back up. Because eventually somebody else starts blocking our email because of the same thing. So, we call up those guys and cut a similar deal. And the problem goes away... for a while. And then the same thing happens again and again. In other words, no matter how many times we work out a deal with someone, another case arises.
It's not just outbound mail. Many customers or customer senders have broken SPF records. Do we reach them all and try to fix those, too? What about the ones who have broken HTML links, broken senders, broken mailers that look like spammers, and so forth? My point is that no matter how many broken things we fix, there will always be more. I'm not sure that it's worthwhile saving the world because it's an uphill battle.
At least, not compared to the alternative. Saving the world is one thing, but what if we accepted that people have broken mailers and just live with it? We don't have to score SPF records super-high in the content filter, nor auto-reject on broken headers, nor reject mail on no A-records in the sender's domain, and so forth. In other words, we can mitigate almost everything by being a little conservative in our spam scoring engine while allowing most of the legitimate mail to get through. While it is true that we are not getting people to fix stuff that's broken, at the same time, we are causing fewer headaches for ourselves.
Saving the world is one thing, but it's very time consuming. And, we have other fish to fry.