IP reputation and the bulk folder

I’ve spent much of today talking to various people about IP reputation and bulk foldering. It’s an interesting topic, and one that has changed quite a bit in the past few months. Here are a few of the things I said on the topic.
Generally IPs that the ISP has not seen traffic from before starts out with a slight negative reputation. If you think about all the new IPs that an ISP will see mail from on a daily basis, 99 out of 100 of those will be bot infected windows boxes. So they’re going to treat that mail very suspiciously. And, in the grand scheme of things, that mail is going to be spam a lot more than it’s not going to be spam.
Some ISPs put mail in the inbox and bulk foldering during the whitelisting process. Basically they’re looking to see if your recipients care enough about your mail to look for it in the bulk folder. This then feeds back to create the reputation of the IP address. There is another fairly major ISP that told me that when they’re seeing erratic data for an particular sender they will put some mail in bulk and some mail in the inbox and let the recipients tell the system which is more correct.
That’s what happens while you’re establishing a reputation on an IP. Once there is some history on the IP, things get a little different. At that point, IP reputation becomes unimportant in terms of bulk foldering. The ISP knows an IP has a certain level of reputation, and *all* their mail has that level of reputation. So bulk foldering is more related to content and reputation of the domains and URLs in the message.
The other reason IP reputation isn’t trumping domain / content reputation as much as it did in the past is that spammers stomped all over that. Affiliates, snowshoers, botnets, all those methods of sending spam made IP reputation less important and the ISPs had to find new ways to determine spam / not spam.
So if you’re seeing a lot of bulk foldering of mail, it’s unlikely there’s anything IP reputation based to do. Instead of worrying about IP reputation, focus instead on the content of the mail and see what you may need to do to improve the reputation of the domains and URLs (or landing pages) in the emails. While the content may not appear that different, the mere mention of “domain.com” where domain.com is seen in a lot of spam can trigger bulking.