Subscription Management Functions long sm_subscribe (char *mailbox); mailbox mailbox name to subscribe This function adds the given mailbox name to the local subscription list, and returns T if successful, NIL if failure. long sm_unsubscribe (char *mailbox); mailbox mailbox name to unsubscribe This function removes the given mailbox name from the local subscription list, and returns T if successful, NIL if failure. char *sm_read (void **sdb); sdb data to use in subsequent calls, or NIL if first call This function returns the local subscription list as null terminated strings. Each call returns the next element in the list. The first call should be with sdb pointing to a NIL pointer; this will be filled in for subsequent calls. At the last call, NIL will be returned.