The Outlook Windows program (not OWA) can be a productive tool once you tweak its UI and learn the keyboard shortcuts for your common tasks. Here are some keyboard shortcuts I find useful:
Ctrl + 1,
Ctrl + 2,
Ctrl + 3: Switch to Mail, Calendar, or Contacts view.
Ctrl + Shift + M: Create a new message.
Ctrl + Shift + A: Create a new calendar appointment.
Ctrl + R: Reply email to just the sender.
Ctrl + Shift + R: Reply email to all.
Alt + S: Send the composed email.
Backspace: Archive the current email or conversation.
Esc: Close currently open email window or any window or dialog.
Ctrl + Eor
F3: Switch to the Search bar at the top of Outlook.
Ctrl + Shift + F: Open the Advanced Find dialog.
F4to search in it.
Ctrl + Shift + B: Open address book to search for people.
Ctrl + Shift + G: Add a flag to current email.
Alt + Downor
Ctrl + .: Switch to next email.
Alt + Upor
Ctrl + ,: Switch to previous email.
Alt + Ins: Clear flag on current message.
Ctrl + Y: Go to a different folder.