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 mail -a "Content-Type: text/html" -s test123 marcus@uncompiled.de < index.html

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$message = "<h1>Hello world!<h1>";
$to      = "empfaenger@system.de";
$subject = "Betrefftext";
$xtra    = "From: ab@sender.de (Ab Sender)
";
$xtra   .= "Content-Type: text/html
Content-Transfer-Encoding: 8bit
";
$xtra   .= "X-Mailer: PHP ". phpversion();

mail($to,$subject,$message,$xtra);

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uuencode index.html < index.html |mail -s "Test" marcus@uncompiled.de

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mail -s "test" marcus@uncompiled.de < index.html