Will e-mail accounts for new customers be separate accounts at Rackspace? Or will they be a part of my account?
As Rackspace require a payment of minimum 10$ per account a creation of new accounts for each customer would result in a minimum payment of 10$ for each every customer. If they would be a part of my existing account at Rackspace the customers would only pay 2$ per email and I would be the administrator for all the customers. So the last one would be far easier to sell to anybody looking for less than 5 accounts.
Reading the wiki and the product pages (both email modules) doesn't explain this particularly well, and it would be nice if you could write some more about how it works. As far I am able to conclude customers will be added to my existing account with me as an administrator, but I am unsure if it truly is so.
Will the modules be able to make the necessary changes on nameservers using DNS Manager? It would make the experience easier for customers if the any necesseray changes in DNS would be done automatically.