74:  Why can't Emacs talk to certain hosts (or certain hostnames)?

  The problem may be that Emacs is linked with a wimpier version of
  gethostbyname than the rest of the programs on the machine.  This is
  often manifested as a message on startup of "X server not responding.
  Check your DISPLAY environment variable." or a message of "Unknown host"
  from open-network-stream.

  On a Sun, this may be because Emacs had to be linked with the static C
  library.  The version of gethostbyname in the static C library may only
  look in /etc/hosts and the NIS (YP) maps, while the version in the
  dynamic C library may be smart enough to check DNS in addition to or
  instead of NIS.  On a Motorola Delta running System V R3.6, the version
  of gethostbyname in the standard library works, but the one that works
  with NIS doesn't (the one you get with -linet).  Other operating systems
  have similar problems.

  Try these options:

  * Explicitly add the host you want to communicate with to /etc/hosts.

  * Relink Emacs with this line in src/config.h:

      #define LIBS_SYSTEM -lresolv

  * Replace gethostbyname and friends in libc.a with more useful versions
    such as the ones in libresolv.a.  Then relink Emacs.

  * If you are actually running NIS, make sure that "ypbind" is properly
    told to do DNS lookups with the correct command line switch.

  * Use tcp.el and tcp.c from Gnus.  This has the additional advantage that
    you can use numeric IP addresses instead of names.  open-network-stream
    currently can't handle numeric addresses.  Brian Thomson
    <thomson@hub.toronto.edu> has a enhancement to open-network-stream to
    allow it to handle numeric addresses.