Building a Defense Against Complaints

Computerworld - I'd like to think that I have a clearly defined role focused around protecting the information assets of my organization. In reality, I also have the delightful job of dealing with whatever else people decide to send my team's way. If I can't think of a better home for it, then we have to mop it up.
This week, we received a complaint from a member of the public. My role as an external-facing part of the company is normally limited. I might get to talk to some auditors and vendors, but that's about it. Even the regulators are all funneled through the compliance department, so on the rare occasion when I'm wheeled out in front of them, I'm accompanied by a compliance handler who keeps me on a short leash.
The complaint came first to the e-mail team, which swiftly passed the buck to the Web support team. That team had the complaint for a day or so before deciding to pass it on to me. The complaining party was a member of an e-mail discussion group about growing rare bulbs. He had provided examples of e-mails from a Hotmail address that he claimed were inappropriate and offensive, and he wanted my company to stop them.
My organization is fairly large, and sometimes remote corners of it take over things without my group hearing about it. But I was pretty sure that we hadn't diversified from financial services to plant advice and that we had not recently acquired Hotmail.
Unfortunately, the complainant had a grudge and an ounce of technical sense. Tucked away in the headers on every Hotmail message is the IP address of the machine that connected to Hotmail and sent the e-mail. This IP address had been tracked back to the address range registered to my company.
The e-mails didn't look that bad. The complainant had posted some obviously off-topic content about the presidential race, and the person connecting from my company had told him to "get a life and stop bothering us."
Given the mild nature of the offending responses, I was almost tempted to send a formal response from my company telling the complainer to "get a life and stop bothering us," but I know that the 10 seconds of pleasure I'd get would be far outweighed by the pain and hassle that would cause.
Since he came to us, I can only assume that the complainant had been given the brushoff or runaround by the discussion group owners and the Hotmail abuse team.