HI All, We have Exchage Server 2013 in our Company.We want to restrict our group in our Server for external users.We can restrict the external users from distribution group property but challenge is we are using Rackspace also as our email server and we have email contact creates for this rs users in our exchange Server.If we restrict external users then RS users also not be able to send emails to our exchange groups.Please suggest how to restricting all external users except RS users of our domain