A lot of healthcare and education institutions use Outlook as well, so I wouldn’t be surprised if mental health or legal uses it too. There may be rules about what kind of client/student/patient information can be sent over email, and often there are healthcare/institution specific variants of the office suites which (are supposed to) meet regulatory requirements

I think the other comment applies regardless. Do work things on the work device/account and let the workplace handle any other concerns. When it comes time to discuss alternatives, you can make a case for something else