Who are you and why are you mailing me?

I’ve mentioned here before that I use tagged addresses whenever I sign up for. This does help me mentally sort out what’s real spam and what’s just mail I’ve forgotten I’ve signed up for.
Yesterday, I received and email from e-fense.com thanking me for my interest in their new product. The mail came to a tagged address, but not a tag that I would have given to e-fense.com. Their opening paragraph said:

First of all, thank you for your interest regarding e-fense and our family of products…

The family of products in question appears to be security and forensics tools. Not something I would sign up to receive information about. The tagged email address points to the eventbee.com website. I don’t have any other email to the address I gave to eventbee. So I’m not sure who this company is or why they think I signed up to receive mail from them.
In all likelihood  this is just some marketer being stupid. I vaguely remember signing up for something at eventbee recently, although I don’t remember what it is, or if e-fense was related to it. After a little investigation, I come to the conclusion this is a stupid marketer that has access to event signup data and added all those email addresses to their mailing list.
I’m willing to give the company the benefit of the doubt so instead of sending a complaint or anything I decide to send them email. I notice the first problem: the visible email address in the footer has a different email address in the mailto: link. I decide to send my question to both addresses, just to be sure it gets to someone who can answer my question. I sent:

Can you tell me what your connection to eventbee is and where you got the email address laura-eventbeeCF at mydomain.com

I discover a second problem. The address in the mailto: link doesn’t exist. The other address seems to have delivered, but I have yet to receive a response from Mr. Vinall. That’s OK, I wasn’t necessarily expecting a response right away.
Then today, I discovered a third problem. They’ve moved to an ESP and are sending out more marketing mail. Daily mail from a sender I never subscribed to? Not good. Daily mail from a sender I never requested email from claiming I signed up to their list? Even worse. I’ve dropped an email to abuse@ the ESP and already gotten a reply. If they are enforcing their policies as their response to me says, then I expect not to hear from them again.
I’ve been around long enough, and I’m willing to cut both the company and the ESP a little slack. But, most normal people would have hit “this is spam” when receiving this mail. In fact, I say email that starts with “thank you for your interest” in a product I’ve never heard of from a company I don’t recognize is clearly spam.
Could this have been handled better? Absolutely.
How would I advise a client to do this better?
Send a shorter email introducing your company to the recipient, tell them why they’re receiving this email and offer them the opportunity to subscribe to your newsletters.

Hi, this is e-fense. You recently signed up for an event at the santa clara convention center. We’d like the opportunity to introduce our products and our company to you. We offer product that does insert product functionality here. If you’d like more information about our company, please visit our website at URL here. If you would like to receive our newsletters in the future please click here to subscribe.

See? Now I know why you’re emailing me. I can look at your product, I can visit your website. I can subscribe to receive your newsletter. Sure, some people might still report the mail as spam, but a lot fewer people will do it now than when you started off unexpected, unwanted and unasked for email with “thank you for your interest in our product…”