PHPMailer - Embed Image

I am trying to embed an image into my body but every time I add <img src="cid:logo"> it shows 500 error. Please see my code below:

        $mail = new PHPMailer();
        $mail->AddEmbeddedImage('logo.png', 'logo');
        $mail->Body = " <img src="cid:logo">Hi this is a test"
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