If you are emailing 10.000 people who signed up for a course of some kind, I think it's no more than logical to inform them when the course will be
IIRC (so don't trust on my memory) you may email those people if they have signed up for your services and you are informing about exactly those services.
However, if you have bought/were given 10.000 random emailaddresses of people who are interested in something you offer but who never actually signed up with your website or bought anything from you, then emailing them would be SPAM. I doubt anyone here will give you advise on how to SPAM
So if you could explain more about the campaign and the addresses, that would be nice. Forgive me if I sound like a smartass, but your initial post sounds a bit spammy
