es copio por un lado el email de rebote completo:

"
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Subject: =?UTF-8?Q?Cambio_de_contrase=C3=B1a:_Noviembre?=
Date: Mon, 6 Nov 2017 14:07:36 +0000
From: Aula Interior Online <info@aulainterior.online>
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Por otro lado el mensaje original

"<p style="color: #333333; font-size: 16px; margin-bottom: 50px;">Hola {{firstname}},</p>
<p style="color: #333333; font-size: 16px;">Te escribo para darte la contraseña del mes de noviembre. Este mes será: <strong> ESnoviembre</strong></p>
<p style="color: #333333; font-size: 16px;">Es muy fácil de recordar, ¿verdad?</p>
<p style="color: #333333; font-size: 16px;">Si aún no lo has hecho, inscríbete en la sesión de hoy. <a href="http://app.webinarclic.com/publico/registro/203/3982" target="_blank" rel="noopener"><strong>Haz click aquí</strong></a></p>
<p style="color: #333333; font-size: 16px; margin-top: 20px;">Recuerda que podrás acceder a todos los contenidos siempre que quieras en <a href="http://aulainterior.online" target="_blank" rel="noopener">http://aulainterior.online</a>, en la sección <a href="http://aulainterior.online/aula-interior-alumnos" target="_blank" rel="noopener">ACCESO ALUMNADO</a></p>
<p style="color: #333333; font-size: 16px; margin-top: 50px;">¡Nos vemos en un ratito!</p>"

Y por último las cabeceras del email que enviamos el lunes 3 de noviembre

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