I managed some domain names for personal and business use. Once in a while, I received offers to my domains which I don't have plan of selling it anytime soon. For a couple of days, I'm received unsolicited emails from different email addresses but with the same contents.

Here's an example of email.
=======================

Hello,
I came across your domain name KING.NET (as example) and I would be interested in buying it from you. Here is my offer, you have to send me a professional appraisal from one of the following companies and I will pay you 85% of the appraise price.

For payments under $2000 I prefer to use paypal. And for larger amounts of money I prefer if we used escrow.com.

I accept appraisals from any of these companies:

(I intentionally remove the URL address of company1 ..3)
- company1
- company2
- company3

If you already have an appraisal from one of those companies please forward it to me, and we will do business.

Regards,
John Doe (example)
===============

I will leave this to you to judge but in my humble opinion, this is a poor way to market their services and I consider it as SPAM.