Maybe you havent got any sales because you are spamming 2.5 million people. No one likes spam...

What do you do when you receive spam? You delete it, don't ya Additionally, you mentioned you're trying to sell advertising. That makes that your target customer should also have a website about a similar topic, or at least be trying to attract your audience, and have a budget to spend on advertising. This is very niche ... advertising to the general population isn't going to do much.

yeah spam is definately not good. try to submit to directories...

You need to gradually build QUALITY traffic to your site rather than waste time and effort alienating potential users.

Try writing some niche articles, and adding original content to your site.

These things, along with hard work are key.

I've highlighted Advertistic's statement, which I believe is very true.
One way to increase traffic to your website is to work for it, by creating some unique content and offerings for your visitors - give them an insentive. If its a product you're trying to sell, make sure everything is accessible, well priced, well thought out - and better than the competition.

Anything else is just general marketing guidelines that are out there for anyone really, I'd suggest searching Google for articles (see, people have written articles that do help people in need, which then generates some quality search engine traffic as a result sometimes.) - I'm sure you'll find some useful tips.

One tip I will leave you with, though, is spamming is not a good idea. Much spam filters these days are advanced enough to recognize quality spam, and the majority of the time users filter out spam on their own as well, so I'm assuming most of your e-mails are going into the trash can of their inboxes.