Auto Welcome Email

I have a membership site using Simple Membership. All members are automatically subscribed to get my e-newsletters.

I also have the option of just registering for e-newsletters without having to become a member.

I want to send an auto Welcome Email when they register for new membership, and a different Welcome Email (with download of ebook) when they subscribe for Newsletter.

How do I set this up please?

Currently my new members are receiving the email that should go to Newsletter subscribers only.