Dear Melanie Leon1,
Good day! Thank you for posting to Microsoft Community. We are glad to assist!
According to your description about "Change the default browser for opening links in Outlook" To understand the situation and be able to offer you relevant suggestions, we would need a little more information from you. Kindly help us in providing the following information.
- May I know your current environment? Is It Exchange Hybrid, on-premises exchange (Exchange server) or pure cloud?
- May I please confirm that you get same situation when default browser is selected under Link handling? To check this kindly open your Outlook go to File-->Options-->Advanced-->Scroll to Link handling then choose Default browser-->Ok then close outlook and re-Open it to check if it will make any difference.
If you don't have this feature kindly refer to Open file links directly in Office desktop apps - Microsoft Support
- Would you mind to kindly provide the screenshot of the outlook version are you using? Kindly go to File-->Office Account
This requested information will help us to narrow down the scenario and find the right troubleshooting.
We are looking forward to your response! Thanks for your precious time. Have a nice day!
Sincerely,
Inema | Microsoft Community Moderator
Hi, sadly I had same issue, so there is my story :-)
Didn't care before realize, that Outlook 2019 is so bad, that there is NOT any options to zoom/fit page to printing borders, if I can call it this way, just lets say to fit a confirmation order in one A4 page without pain, copying to word and fight with stupid tables :-).
So i found, that there is a way, how to view email in browser,

and what i did o god... When I opened mail in new window by double clicking on it in middle row, and when I stupidly click on "Action menu" -> "View in browser" in that upper bar in middle, there jumped on me a menu with option to choose browser, so a chose Vivaldi Browser, and it does show just a source of that page, so decide to change it and then I realized, that i cant find that option even in "Generals" even in "Advanced"

I was sad, spend quite a lot of time to find this!!!
Oh damn, but, after I opened mail with Vivaldi again, just look, what I will find inside, I realized, that there is file extension, called ".mht" in web/file address looks exactly like this "C:\Users\USER\AppData\Local\Microsoft\Windows\INetCache\Content.Outlook\MT41OOTG\email.mht"
So last hope came to my mind, to try file associations and what i found, a SOLUTION :D :D :D
I went to windows settings, gets to Apps, chose a Default aps and Set defaults by apps:

after a chose a Vivaldi app, and later realize, that Internet Explorer or Edge have a same "handlings", so doesnt metter what you chose :-).
What I chose as a browser you can see on screenshot :-).

And even without restarting any of browsers or outlook a tried View in browser again:

AND IT WORKS!!!!!
Opened in old pure Internet Explorer 11 on Windows 10, with superb options for printing, eh "FIT TO PAGE", yeeehaaa!!!!
And this is my story, tell it to every one please! It was a long journey :D :D :D
No really it tooks me a few hours of googling and trying to find solution, I even thinks about to delete my profile in Outlook, luckily i didn't , uff... and sorry for Czech screenshots, I live there :-). I even want to put some screenshots how nicely it looks, but everywhere was personal informations so nope ;-).
Also funny is, that all this starts, because I want to buy a new keycaps and I just want to PRINT whole order to one page :D
Also expect, that every time, when you open IE11, popups annoying Edge and wants you, begging to use it, just close it, and when you open IE first time, it will asks for security settings, where i chose a red shield, because I will use it just for PRINTING from Outlook.
So here is my story and I hope, this will helps to a lot of people ;-)
dim0n