I think all those methods are good -- for snail mail. Which is how you should start.
The law is clear, and this is what I tell my clients: you cannot send cold email to any number of addresses that have not signed up to hear from you.
That's the very definition of spamming, and the federal law that forbids it is the CAN-SPAM Act.
What you can do is this:
1. Presumably you've identified a problem this audience has that you can solve, so develop a resource - white paper, video, whatever - you can deliver electronically.
2. Send this list a sequence of three postal mailings that drives them to a single page where they can download this resource.
This is called a landing page, and it should contain ONLY information that sells the resource - and a form that collects email addresses.
It should not have any site navigation, or any other information - just the info about the resource, and the form.
The form needs a bit of language telling them that by hitting Submit and downloading the resource, they give you permission to send them email.
When they hit Submit, the next thing they should see is a prompt to check their email. (NOW you have permission!) Also, for your own purposes, you want to make sure they didn't just sign up with email@example.com.
In that email, finally, you reveal the link to a second page - the one with the actual download link. This one can have your full template, if you like, and suggest posts or pages they might want to explore next.
Best of all, you now own the fully valid, double-opt-in email address of a qualified prospect. who might even read your next email, and probably won't report you for spam.
This method will not give you the emails of everyone on the original snail-mail lists you rented. You'll probably get a response of well below 2%, perhaps as little as 0.5% (50 basis points).
That's why it's not a good idea to judge success or failure by response rates, btw. If, after three mailings, you've got 100 or so qualified email subscribers, and a few of them become customers, you will have grossed more dollars than you spent on the promotion - mailings plus the web work.
And if you further have other things to offer your new customers - so you can develop a long-term relationship to leverage, and build the lifetime value of that relationship, that first set of three mailings will have been profitable indeed.