Can you add a link to an image instead of uploading through the editor

I was wondering if there is a way to code into a template, the option to define a link to an image already on the web instead of uploading. I wonder because we do a lot of html emails that the images already exist on our site and in the same format for our internal emailing system. It would be nice to have the option to "choose" from your desktop or put a direct link to an image. Anyone have any advice or know if this is possible?
Thanks!

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