Pos yo obligaría a los usuarios del smtp a autentificarse.
Y si te quieres poner a mala leche, deniega el acceso a esa ip. :-P :-P
Más datos de la IP:
% This is the RIPE Whois server.
% The objects are in RPSL format.
% Please visit (link roto) for more information.
% Rights restricted by copyright.
% See (link roto)
inetnum: 217.15.34.128 - 217.15.34.159
netname: CANALMAIL
descr: CanalMail
country: ES
admin-c: JC355-RIPE
tech-c: LT124-RIPE
status: ASSIGNED PA
notify: hostmaster@idatahouse.com
mnt-by: IDH-MNT
changed: nsommer@idatahouse.com 20020111
source: RIPE
route: 217.15.32.0/20
descr: Internet Datahouse
origin: AS15734
notify: nsommer@idatahouse.com
mnt-by: IDH-MNT
changed: nsommer@idatahouse.com 20001110
source: RIPE
person: Javier Camara
address: Paseo de la Castellana, 163, 4º dcha
address: Madrid
phone: +34 91 270 12 20
e-mail: Jc@canalmail.com
nic-hdl: JC355-RIPE
notify: hostmaster@idatahouse.com
changed: nsommer@idatahouse.com 20020111
source: RIPE
person: Luis Tejeda
address: Paseo de la Castellana, 163, 4º dcha
address: Madrid
phone: +34 91 270 12 20
e-mail: Lt@canalmail.com
nic-hdl: LT124-RIPE
notify: hostmaster@idatahouse.com
changed: nsommer@idatahouse.com 20020111
source: RIPE