t h, as defined by RFC 2965, section 1.

The reach R of a host name H is defined as follows:

   *  If

      -  H is the host domain name of a host; and,

      -  H has the form A.B; and

      -  A has no embedded (that is, interior) dots; and

      -  B has at least one embedded dot, or B is the string "local".
         then the reach of H is .B.

   *  Otherwise, the reach of H is H.

>>> reach("www.acme.com")
'.acme.com'
>>> reach("acme.com")
'acme.com'
>>> reach("acme.local")
'.local'

r‡