Is there a way to get email notifications when someone responds to the thread I started?

Or email notification to any thread I am involved in?

Look at the email options in your preferences.

There's both a place when you make a post in the full editor to "add to followed threads", and a place in your preferences.

However, it doesn't always work. I've only gotten a few notifications and only to find out there have been replies in others that I didn't get. It seems very random.