I'm not an expert on this, but two things I've found cause problems are
Using BCC to send the email. These would end up in the bulk messages folder on Hotmail. Not sure if they do anymore. As you're sending personal emails there's no need to do this (and you probably aren't anyway, but thought I'd just mention it).
Using a dodgy SMTP server. This can include sending emails out through your host's SMTP server if your host hasn't been sufficiently careful about preventing spam in the past (e.g. mandatory, verifiable double opt in policies). If this is a problem, you could think about getting
Google Apps for your domain, which will also give you a shiny Gmail account.
In all this, I've of course assumed your emails are legit and don't look spammy by including (for instance) links to college loans as you do in your site sidebar.
Hope that's useful. Your training site looks good, by the way.