I logged the $MAIL_MIME variable in the sendmail.inc file before the // Begin SMTP Delivery Block if someone can see anything wrong here maybe (I changed the sender/receiver data):
Mail_mime::__set_state(array(
'_txtbody' => 'testing',
'_htmlbody' => NULL,
'_html_images' =>
array (
),
'_parts' =>
array (
),
'_headers' =>
array (
'MIME-Version' => '1.0',
'Content-Type' => 'text/plain; charset=US-ASCII;
format=flowed',
'Content-Transfer-Encoding' => '7bit',
'Date' => 'Tue, 13 Jun 2017 13:37:07 +0200',
'From' => 'sender@domain.com',
'To' => 'email@example.com',
'Subject' => 'test',
'Message-ID' => '<7f16f602217ceb410627eb9628d4389c@pegasus-yachts.com>',
'X-Sender' => 'sender@domain.com',
'User-Agent' => 'Roundcube Webmail/1.2.5',
),
'_build_params' =>
array (
'head_encoding' => 'quoted-printable',
'text_encoding' => '7bit',
'html_encoding' => 'quoted-printable',
'html_charset' => 'UTF-8',
'text_charset' => 'US-ASCII;
format=flowed',
'head_charset' => 'UTF-8',
'eol' => '
',
'delay_file_io' => false,
),
))