Well if you are successful accessing your Outlook email via the Apple Mail app, then it certainly points to Safari to being the culprit. As such, trying another web browser (I suggest Brave) and the issue does not reoccur, then we know something about Safari is not right.
... and yes, there are a number of ways you can access email with your Mac:
- Via a web browser.
- Via the Apple Mail app.
- Via the Microsoft Outlook app.
- Via dozens of other third-party mail apps.
One note of caution, with the Microsoft Outlook app. I believe this app is now a part of Microsoft's "new" Outlook; whereas, the "classic" app is still available. This issue with the new version is that any non-Microsoft email accounts you configure to use with it, will send/receive messages through the Microsoft servers before/after going to/from the third-party source servers.
That means, for example, if you configure the new Outlook app to be able to access your iCloud or Gmail mail, those messages will pass through the Microsoft servers. The classic version did not do this and messages went directly from the mail app to the third-party (iCloud or Gmail) servers directly.
With that said, I suggest that you avoid the Outlook app, and either use another web browser or continue to use Apple Mail to access your Outlook messages.