The first thing is to familiarise yourself with the CANSPAM act (Mr Google will be able to advise here). One of your major stumbling blocks will be the fact that you are working off a freebee email account - with 7000 active clients you might consider a company email account - there are many hosting companies out there (you mention AtomPark) , but I can recommend MBD Solutions (
www.mbdsolutions.com). These hosted email companies will have registered their servers with the main ISPs etc.
A very good guide to email marketing can be found courtesy of MailChimp. (
http://www.mailchimp.com/articles/em...rketing_guide/). They are reasonably priced and I find their style refreshingly approachable.
I should probably add here that there are a zillion companies out their offering these services. I use both the companies mentioned above but have no form of affiliate program in place. As with all things in life, do you own research and take you own responsibilities.
Hope this helps
James