One of the great "Getting Started" features of Cast98 is that transitioning is a total sinch. As a member studio, you get access to a handful of email templates that you can customize and send out to folks at critical junctures in your production cycle.
Here's a list (current as of 26 Jan 17) of the email templates Cast98 provides:
I (Daniel) would love to help you write any email that you need to send out to your cast members or performers, so don't hesitate to send me new ideas for email templates to include on Cast98.
Sending email to hundreds of performers in one foul swoop is a big responsibility. There are legal implications if such digital communications are not handled carefully. Cast98 could be blacklisted if any one director gets crazy with sending emails and recipients start marking messsages as spam, and that would ruin the fun for everyone.
Instead, these copy-and-pastable email templates give you (the director) flexibility to use whatever email service you want when communicating with your performers. Just make sure to use the BCC line to drop in your recipients' email addresses. That's just one step you can already take to protect your performers' privacy rights.
When Cast98 is able to put together a team to manage the procedures and enforce security rules to protect performers' privacy, it'll the trusty ol' blog here will let you know.