In the comments of the last post, Gary DJ asked an insightful questions and I think my answer probably deserves a broader audience.
How can ESPs honor unsubscribe requests from ISPs without FBL programs (read: Yahoo!) if senders are not aware that subscribers are asking to be removed (via “Mark as Spam” links)? Yes, we can tell which clients are “good” and which are “bad,” but will continue to send to that Yahoo! recipient until we know better.
I think the disconnect here can be boiled down to: is your goal to send mail people do not complain about or is your goal to send mail that actively engages and interests your recipients? If your goal is to send mail that people don’t complain about, and thus get into the inbox at ISPs, then you are going to see problems with ISPs that measure user response and do not provide a FBL to senders. If your goal is to send mail that actively engages and interests your recipients, then you do not need the FBL in order to avoid being blocked.
I agree it would be nice if ISPs were to provide a FBL to all senders, but realistically, that is not going to happen. So you need to look at the data you have about your mailings (or as an ESP about your customers’ mailings) and make reasonable assessments of how the recipients are responding to the mail.
If the mail is being received badly, then the sender needs to take a step backwards and look at their overall email marketing program. One of the things I hammer into clients is list hygiene. Keep those lists clean. One way to do that is have a set process for engaging users after some period of time of inactivity. If you are actively only mailing people who are engaged and responsive to your mails, and purge off people who never click or never open a mail, then those Yahoo users that you mention will eventually be removed from your list.
If your Yahoo complaints are so high that you are getting blocked, you have bigger issues. Again, step back, look at your program and focus on relevancy and engagement.
Send mail that is relevant, send mail that your users want and, generally, you will not see complaint based blocking.