I went to mailermailer.com (years ago), got a script to put on my site letting people sign up, they opt in, mailermailer handles all of that, and I have a nice list for my newsletter, which mailermailer sends out and if there are any complaints, they handle it.
Getting a list the way you describe isn’t a good idea, it’s not targeted, people aren’t opting in for your mail and it just results in spam and spam reports.
You want to send your stuff to people who want to see it. That way everyone is happy and you’ll actually see some results.