This wouldn't be bad if I could uninstall that app but the button is gray on my machine. Same for the Xbox apps that I am guaranteed to never need. Weird feeling.
Open the PowerShell as admin and copy:
Get-AppxPackage * windowscommunicationsapps * | Remove-AppxPackage (remove space at the two asterisks, HN turns the text into italicized)
voilà, Mail and Calendar uninstalled. You can do this with all of the preinstalled stuff (Xbox as well), see the link above.