Don't take my subscribers away!

Tom Sather has a good summary of the problems with inactive email addresses and why data hygiene is critical to maintain high deliverability. These recommendations are some of the most difficult to convince people to implement.
Some of my clients even show me numbers that show that a recipient that hadn’t opened or read and email in 18 months, suddenly made a multi-hundred dollar purchase. Another client had clear numbers that showed even recipients that didn’t open for an entire year were responsible for 10% of revenue.
They tell me I can’t expect them to let their customers go. These are significant amounts of money and they won’t let any potential revenue go without a fight.
I understand this, I really do. The bottom line numbers do make it tough to argue that inactive subscribers should be removed. Particularly when the best we can offer is vague statements about how delivery may be affected by sending mail to unengaged users.
I don’t think many senders realize that when they talk about unengaged users they are actually talking about two distinct groups of recipients.
The first group is that group of users that actively receive email, but who aren’t opening or reading emails from particular senders. This could be because of their personal filters, or because the mail is going to the bulk folder or even simply because they don’t load images by default. This is the pool that most senders think of when they’re arguing against removing unengaged users.
The second group is that group of users that never logs in ever. They have abandoned the email address and never check it. I wrote a series of posts on Zombie Emails (Part 1, 2, 3) last September, finishing with suggestions on how to fight zombie email addresses.
Unlike senders ISPs can trivially separate the abandoned accounts from the recipients who just don’t load images. Sending to a significant percentage of zombie accounts makes you look like a spammer. Not just because spammers send mail to really old address lists, but a number of spammers pad their lists with zombie accounts in order to hide their complaint rates. The ISPs caught onto this trick pretty quickly and also discovered this was a good metric to use as part of their filtering.
I know it’s difficult to face the end of any relationship. But an email subscription isn’t forever and if you try to make it forever then you may face delivery problems with your new subscribers.