You can't embed magazines with an iFrame or Javascript code in an email. That's why you need to share a link to your magazine.
To get the link of your magazine, go to "My Publications".
Then click on the cover of the magazine you want to share.
You will get the preview link to the magazine. You can either share that link or the direct link you receive by clicking on the "Read" button.
Sharing from the preview mode:
Sharing from the fullscreen mode: