The Domain Business - Want domain X Inquiries?

I have a few domains, maybe 500 to support the business. 

Most days, I get an inquiry like this one:

--------------------------------------

Tracy S****man <tracy****man@yahoo.com>	1:50 AM (12 hours ago)
to john

Hello,

I think that you are the owner of a similar domain name and I am wondering if you would like
to obtain the mytime4learning dot net from me?

Thank you for your time and have a nice day.

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What do I do with these emails?

I often ignore them but then they keep emailing for awhile.

I sometimes am interested and then my first step is to see if the domain that they are offering is available. Often it is. So I ignore the approach and go get the domain directly from a registrar for $7 per year.

In rare cases, I go back to the vendor and try to agree upon a price. In some cases, we've done a deal. But in most cases, they hold out for what I think are absurdly high valuations so we negotiate for awhile and then it falls apart. I try to NEVER talk to them on the phone or let them get my direct line since many of these people are like mosquitoes, once they find you, they just keep at it.

There's another email that I get less frequently (which I can't seem to find a copy of right now).Typically, it's from a major foreign country and they say that someone has tried to register a name like mine (Time4Learning.china.co) and to help me protect my copyright, they would offer it to me first. So for $xyz, I can have it but I need to act fast.

I've never ever answered any of those emails.

Your experiences with this?

Managing & Parking Unused Domains

Here's how I try to use my domains to help build traffic for SEO purposes. Examples (from my netfirms accounts):

Books Count - A url intended for our future reading program. Initially used as a parking place for the spellingcity software development effort. It's been one of my domains for over a year and about 11 months ago was populated. Since we wanted to be under the radar, it has no links. This posting is the first link to the site! Bookscount.com

Family Homeschool - This little 5 page website is put up with a site builder. It's unfinished. Nevertheless, the site has a google pr of 3! go figure. Familyhomeschool.org

Homeschool curriculum review - Another quickie website with a few pages of html that seems like I created it in word. It has good content and the right links and a google pr of 3. Why? Homeschool-curriculum-review.com. With it's strong url, I could alot with this one.

Homeschool Curriculum - This domain has no page rank, it is forwarded to homeschoolonline.org. homeschool-curriculum.biz

This approach of treating them one-by-one is kind-of fun and it is not the type of seo-work that the algorithm gurus at google are likely to care about. But, it's time-consuming and perhaps not very effective. Since I have a total of 150+ domains, is there a better way?

Previous Posts related to domain optimization (interesting to note how little progress I've made in this area despite having grown my number of domains to 150):
Parking domains for profit, is there a free lunch with domains?
Parked domains, how best to use them?
Useful Parking of Domains