Have tried this code too (with the correct image) but it just breaks my homepage.
You didn’t provide the “this” code you’ve tried, and you didn’t provide your homepage URL. So there’s nothing for us to check for you.
These preview images are fetched from something called “OpenGraph” code on your website. Yoast generates and inserts this OG code into your site.
As long as your site has the correct OG image code, there’s not a whole lot you can do about this.
That’s because “consumers” (the social media sites where you share links) will fetch the image and cache or store it on their servers for some time, so they don’t have to fetch it every time that same link is shared… just to speed up things.
This creates the kind of problem you’re having now… when you change the image: the sites will continue to show the old image until their cache time-out expires and they re-fetch the image.
Site’s like Facebook and Twitter allow you to clear the cache (see Facebook Sharing Debugger and Twitter Card Calidator, forcing a re-fetch of the image (and all other link information). But I don’t know about Outlook!
