I was just reading a blog (Your Home Sold in 120 Days Guaranteed OR) where agents were talking about how agressive a particular training program is in follow-up emails and they couldn't get off the email list. Here's an easy way to stop all the spam mail.
1. Set up temporary email accounts that forward to your primary account. You can do this via P2A's email account management. This is useful when you think you "might" want to continually receive emails from the source. So, for the XYZ service, create an "xyz@<yourdomain.com> email account that forwards to your prime account. (Or, for any other service -- <servicename>@<yourdomain.com>) I did this when signing up for the Proctor information and then deleted it after I got what I needed -- so, no spam from that company 
.
2. Get a 'free" email account -- like hotmail.com -- when you're asked to give an email to receive information that you only want to receive one time, use it. Hotmail has a capability to send all email except those on your contact list to the junk folder where it can be deleted immediately or held until you delte it. I normally have it set to delete immediately except when I'm expecting an information email.
3. If you put your email address on your website:
a. if you don't need them to click on it to send you an email, put a space in the address -- mine might look like: nick@park city sold.com, or
b. if you want them to click on it to send you an email, use the concept in para 2. Then delete/change it if you start to get spammed. Idea for these email usernames are info, information, customerservice, custsrv, help (e.g. info@<yourdomain.com>).