Go back to "Default Programs" in Windows, choose "Set Default Programs", choose "Opera" and click "Set this program as default". Then, click on "choose defaults for this program" and make sure all the protocols and file types are selected for Opera.
If that doesn't work:
Download the offline package of Opera from https://www.opera.com/download.
Goto the URL opera://about and take note of the install path.
Uninstall Opera via programs and features while choosing to keep your data (if you want to keep your data).
After Opera is uninstalled, delete the install folder if it still remains.
Launch the offline package installer and click "options". Set the "install path" to "C:\Program Files\Opera", set "install for" to "all users", uncheck "import data from default browser", check "Make Opera the default browser" and install.
Then go back to "Default Programs" in Windows and make sure Opera has all its defaults.
Then it should just work. But, to test that things are correct, open a command prompt and enter this command:
start "Test" "https://www.example.com/"
It should then open in Opera. If you get asked what app should open the URL, selected "always use this app" and select Opera.
Try the same thing with:
start "Test" "http://www.example.com/"
If those both open in Opera, then Opera is configured correctly. If Opera still doesn't open from Outlook, I'd blame Outlook.
You can also go into Default Programs and choose to set a default by file type and choose the https and http protocols and set them to Opera.
@kaatula said in Web link in email does not open in Opera the default browser:
When I try to open links from my default Windows 10 Mail Program, I see the "Unable to open https://....." dialog box.
I have Windows 10 Pro 1809. I use Mail 16005.12527.20152.0 mail client.
I tried in the Mail app (version 16005.12527.20152.0) on Windows 10 OS Version 1909 (Build 18363.657). While Chrome was the default, when I clicked on a link in an email, it asked me what app I wanted to open the link with and Opera was a choice. When I set Opera as the default browser in settings -> Apps -> default apps in Windows, the Mail app didn't asked me and just opened the link in Opera.
Could just be a bug with the Mail app on the older build of Windows 10 you have. Not sure.
My Opera is installed to "C:\Program Files\Opera" and was installed with the "All Uses" option (that you get to when you click "options" in the installer), FWIW.