I've been selling domains for about 11 years now and 99.9% to end users. Most in the 1-10k range with a few below and a few above that range. Quality domains that make business sense helps keep a natural flow of inquiries on my desk every week. I have listed at Sedo, DomainNameSales, Afternic etc... over the years as well as extra eyeballs never hurt although most deals are done direct as I redirect sales links to my own site which has built me a 11 year old end user database with some repeat end user buyers in it.
When a buyer comes to you first the decision has already been made they want the domain all that remains is negotiations to see if the numbers align to make it happen so a Hot lead with more ROI and a higher success rate.
When you email it shows you are looking to sell and brings it down to door to door sales level as your hitting Cold leads which results in less ROI and a lower close rate. Not only do price negotiations have to take place but you also have to convince them why they need your domain as they didn't get off their couch to come and look for it so even if your hitting related industry leads most have no understanding of the internet, domains, hosting etc... as they just pay someone to handle it.
Can contacting end users work=sure the problem is that so many people spam shit you'll be lucky if it ends up in their inbox, then ya gotta explain why they need the domain, then your price has to be cheap cause your soliciting them, etc...
I prefer the combo of buying quality domains and using the distribution channels that have been created to get the eyeballs on your inventory, DomainNameSales/DomainTools, GoDaddy/Afternic, your own site, etc... as ROI and close rate are both definitely higher when they knock on your door first. I highly doubt I could have sold some of my $8 acquisitions for $6500, $7500 etc... by emailing cold leads, those big returns happened from end users that understood the internet and knocked on my door first as basically 99.9% of the domains I own were all $8 expired pick ups that still clear 1-10k based on quality of the domain/distribution channels and patience. If a domainer owns hundreds of domains and is using distribution channels and never gets an end user knock on their door first the question should be do I own shit instead of should I email end users as domain quality and distribution channels that exist are the biggest factors to natural success.
http://www.business.ftc.gov/documents/bus61-can-spam-act-compliance-guide-business