OAuth with Twitter and follow up


I have a website that authenticates users with Twitter via OAuth. I need a way to contact users after they registered.

What are my options?

There is no email in OAuth result and “Read/Write/Direct Messages” looks scary. As I understand an OAuth application cannot send a direct message to a user with Read-Only permission.

Is my only option to have users follow me? Is there any way to required that users follow my application as part of the OAuth process?