Over on the Word to the Wise blog, Laura Atkins answers the question, is it wise for senders to block mail to various anti-spam companies? Read on for my take on the practice.
I've never advised clients to avoid sending mail to domains owned by the various anti-spam device/service companies. Why bother? If they have a spamtrap network, it's not likely to be on their corporate network. (If they're smart, and most of them are.) Also, if you think that avoiding their corporate domain means that you'll never spam anybody that works for that company, think again. They, like everybody else in the world, has a webmail account or two that they use for various things. Avoiding companydomain.com won't keep you from spamming the CEO's Gmail account.
It might sound a bit simplistic, but the best way to stay off of these guys' radar is to NOT SEND SPAM. At my last job, a client would occasionally spam an employee at a big ISP or anti-spam filter vendor, which would result to a spam complaint getting escalated to me or somebody else on my team. Addressing one of these complaints was pretty straightforward: Prove that the person opted-in, or recognize (and admit) that you've got a policy enforcement issue, and that a client needs to be sanctioned for doing something they shouldn't have.
Laura also mentions AOL, which reminds me of a story. About a hundred years ago (actually, somewhere around 2001), I received a call at work from a friend at a rather large ISP, somebody who decides what mail gets to the inbox, and what mail gets blocked. They were reporting spam from a client of ours, and was giving me an opportunity to respond to their complaint before blocking all mail from that client.
I investigated and found that not only was the signup legitimate, it was a confirmed opt-in (double opt-in) process. The signup was legitimate, and I had all the data associated with that signup, including IP addresses and timestamps. Showing them that data, they remembered that oh, yeah, they really did download that software package (which had a clearly labeled opt-in/opt-out procses), and oops, nevermind, not really spam.
Spam complaints happen. Instead of trying to avoid sending to certain people, it seems to me that it would be better to make sure your signup practices are solid enough to withstand scrutiny that comes along with the occasional escalated complaint from somebody important.