Mass e-mail: Problem to get a new languages

Hello,

i translate de last version of Mass e-mail to Spanish languages. I translate from mass-mailer.pot file with Poedit program.

I verified mi define ('WPLANG', 'es_ES'); is on my wp-config.php

I copied the translate files to languages dir , but i am not sure the name of this one to Spanish (es_ES), because don´t get the Spanish languages, i test it with the next file names:
es_ES.mo
mass-mailer-es_ES.mo
mass-mailer_es_ES.mo
mass-maileres_ES.mo

Please, Witch is the correct name?