_expand_hostname =head2 _expand_address

Usage     : @expanded = _expand_ip($ip); # For example
Returns   : Given an ip, hostname, or e-mail address, it will expand
            that into the "appropriate lookups" which sendmail would use
            (e.g., given '192.168.1.2', _expand_ip would return
            192.168.1.2, 192.168.1, 192.168, and 192)
Argument  : The IP Address, hostname, or e-mail address to expand
Throws    : 
Comments  : 
See Also  :