Código PHP:
# TAG: visible_hostname
# If you want to present a special hostname in error messages, etc,
# then define this. Otherwise, the return value of gethostname()
# will be used. If you have multiple caches in a cluster and
# get errors about IP-forwarding you must set them to have individual
# names with this setting.
#
#Default:
visible_hostname localhost
Copiado desde archivo de configuración, si la linea no existe tendrias que agregarla.
Un saludo.