To view the source of an email in the Mac OSX program “Mail”, select the message and look at the top menu.

Select “View” >> “Message” >> “Raw Source”.

If you copy that source and paste it into a new HTML file, you will have a mish-mash of un-working parts. Apple’s Mail program inserts a lot of extraneous code that you won’t need in sending an email of that sort.

To start off, find the part of the source that says “” and copy from there to . Delete the rest.

Then, in the code, do a search for “3D” (case-sensitive) and delete all instances.
Then search for ” =” and delete all instances.

Apple Mail inserts these to replace characters that might get confused otherwise, but they’re generally useless to other email clients, and they break your HTML.