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<matamala@medialife.es>: host mail.medialife.es[146.255.98.200] said: 550 5.7.0
    HELO argument [localhost.localdomain] is malformed. See
    http://spamauditor.org/best-practices/valid-helo-identifier/ for more
    information. Protection provided by MagicSpam 2.0.11-1
    http://www.magicspam.com (in reply to RCPT TO command)
Reporting-MTA: dns; localhost.localdomain
X-Postfix-Queue-ID: EE3038AF7F
X-Postfix-Sender: rfc822; info@medialifeonline.eu
Arrival-Date: Thu,  7 Sep 2017 16:28:58 +0000 (UTC)

Final-Recipient: rfc822; matamala@medialife.es
Original-Recipient: rfc822;matamala@medialife.es
Action: failed
Status: 5.7.0
Remote-MTA: dns; mail.medialife.es
Diagnostic-Code: smtp; 550 5.7.0 HELO argument [localhost.localdomain] is
    malformed. See http://spamauditor.org/best-practices/valid-helo-identifier/
    for more information. Protection provided by MagicSpam 2.0.11-1
    http://www.magicspam.com
Asunto	Prueba de correo
De	info@medialifeonline.eu
Destinatario	matamala@medialife.es
Fecha	Hoy 18:28
Esto es una prueba de email

A ver que tal va la cosa