Be realistic. I'm not going to be able to spot anything in your code.
The approach I would take to solve this is as follows.
1) Write out the HTML to a file, before you put it into an email. Check the HTML is valid by opening it in a browser and maybe using a HTML validator. If this is working fine, you know it is not the problem.
2) Send the email with the embedded HTML, but all images with SRC to external images hosted on a website. If this is working, you know the basic HTML email is working correctly. Since there are no embedded images, this can't be the problem.
3) Send the full HTML email including the embedded images. Now open this using a range of mail clients, including Outlook, Thunderbird, Gmail etc. This will check if it is just a bug in a specific mail client.
The only way to identify and solve the problem is to work through it meticulously.