At this moment, Virtuagym does not support mass-email. It is possible however to export your client list to excel or as a CSV file. From that, you can extract the email addresses and use a program like MailChimp (free up to 2000 receivers) to send a news letter.
Virtuagym also supports two other ways to reach your clients: You can either send all your clients a message through your inbox, or write a blog on the online community. Your members will receive an email that there is a new message/blog, so they will be able to view it easily.