Hi Mariette,
Unlike web page, javascript and iframe will be blocked in email by most of email service providers due to security protection.
But you could take following method as reference if you would like to embbed a map in marketing email for your contacts.
1. Create a Bing map account at Bing Maps Dev Center.
https://www.bingmapsportal.com/
2. Finish your personal profile(you can sign in with crm mailbox directly)

3. Create a key to use Bing map

Settings of a key

A new key:

4. There is a helpful website: https://staticmapmaker.com/, which can generate a static map(actually an image) in html embbed format code. Bing is one of supported map.
Just apply the key to API Key field,
add longitude and latitude of your location, e.g: find Shang hai center
Google shanghai center longitude and latitude

You can zoom it to a proper size and a pin on map to point out location.

5. Finally copy HTML embedded code in marketing email. (Or copy image's src directly and paste it to an image element src)

Regards,
Clofly