Hi,
I think I found something for you. I re-created the problem on my Evo test system.
Try this:
Elements... Manage Elements... Plugins
Buried in the list, click "Tiny MCE..."
Click "Configuration" tab, and scroll down to "Path Options", and choose "fullpathurl", and Save.
I’ve never seen this before. But it worked great for me.

Oh, and in case it matters, in the MODx config, I have Tiny set to use "Custom" theme.
Email newsletters are a special very weird breed; one must use HTML circa 1995, I have never been able to use a HEAD section to work in all email systems, and all styles must be inline, I know, it’s crazy!
How to do all this in Revo? No idea whatsoever.
Cheers, Dave