In addition to Outlook, Windows has a program called “Mail” that is set as your default email program if you don’t change it on purpose.
For me, this led to a lot of puzzlement. Even after I had figured out how to turn off notifications from Mail (because messages I thought I had already read kept firing alerts onto my screen), I was still getting launched into Mail when I clicked an email link. This was super annoying because my email signature was set up in Outlook, not Mail.
As light dawned over Marblehead, I realized that this was because Mail thought it was my default email program. If you’re in that situation, these easy instructions from Lifewire will help you set Outlook as your default email program.