Subscriber classes specify values that allow a voice application to control
the use of mailboxes. Each subscriber class can specify different value for:
- The maximum number of mailboxes that can be assigned to guest users
- The maximum number of messages that a mailbox can accept
- The maximum number of distribution lists that can be constructed for each
mailbox
- The maximum number of entries in a distribution list constructed for any
mailbox
- The maximum record time per message
- The maximum number of greetings that the mailbox owner can record for
a mailbox