Office 365 email accounts will default to reply all when replying to a message instead of replying to the sender only.

This is a bad practice, especially since it’s not the expected behavior of an email client. When you receive an email, the default has always been to reply to the sender only.

I’ve made a short screen cast showing how to change this behavior.

Set Office 365 to reply by default

  1. Click the Gear icon in the upper right corner.
  2. Click Options (Do not click Office 365 Settings.)
  3. Click Reply settings in the menu on the left. It’s the second-to-last option under Mail.
  4. Click the option next to Reply.
  5. Click Save. If you don’t click Save, it won’t take effect.
  6. Click the <– Options link at the top of the left-side menu.

Now you can reply to emails as you always have. And Reply All is still accessible from the drop-down menu in the message.