I get a lot of calls from senders who tell me that they have not changed what they were doing, but all of a sudden their mail isn’t performing the way it used to. Sometimes it’s simply less effective marketing, but more often than not the issue is mail being blocked or filtered to the bulk folder.
What worked today won’t work tomorrow. Spammers are forever evolving new techniques to get past spam filters. ISPs are forever evolving new techniques to stop them.
One of the current driving forces for spam filter development is focused on the individual recipients. Recipient wants and needs are king in the world of ISP mail filtering. Much of that is driven by the underlying business models of the free ISPs. They are selling eyeballs to their advertisers and that relies on keeping as many eyeballs around for as long as possible.
An early version of the recipient driven filtering was “add to your address book” where individual users could over ride ISP delivery decisions by actively adding a From: address to their address book. The ISPs have been refining this over time. For instance, if you reply to an email in some clients, you are prompted to add that address to your address books. If you take an email out of your bulk folder and move it to your inbox then that address is automatically added to your address book.
But the refinements haven’t stopped there. ISPs are now making smart decisions about what emails a particular recipient will want to receive. This raises a number of challenges to senders. How do you send email to ten thousand or a hundred thousand or a million people and make it relevant to all of them?
Smart senders will take the individual delivery challenge in stride. They will change along with the ISPs, to send mail that their recipients want to receive. Change is inevitable and required.

filtering • opt-in • relevance • spam filters