[BetterRed]

@maurices5000 - see attachment

1. Starts with a MOBI named 'People Eating Cuddly Creatures' in the Mobipocket Reader
2. I change the Title to 'People Eating Marsupials' in the calibre Metadata editor
3. I run the Embed Metadata tool (ctrl/e), select the MOBI, and hit OK
4. Ends with a MOBI named 'People Eating Marsupials' in the Mobipocket Reader

Now I can email the MOBI - but I don't use calibre's email facility, so I'll stop there

If that doesn't work then I must be misunderstanding what you're wanting to do.

BR