HTML template with image


I’m trying to make a HTML template that includes an image.
First I tried to embed the image in base64 directly in the img src field, but it’s not supported by outlook.
So I made a template with all the needed MIME parts.

However, when the scrip send the template email, every part is modified to be text, so my header is modified from
Content-Type: image/jpeg; name="image001.jpg"
content-type: text/plain; charset=“utf-8”; name=“image001.jpg”

I found that this is done in lib/RT/Action/ in the Prepare sub, just after the following comment :
# For security reasons, we only send out textual mails.

So before changing it I would like to know what the security reasons are.

Thank you,