The automatic reply answers incoming emails automatically, e.g. during vacation. With a time range, it turns on and off by itself.
Outlook (classic)
Choose File › Automatic Replies.
Turn on Send automatic replies and optionally set Only send during this time range with start and end.
Enter the text for Inside My Organization and Outside My Organization.
Confirm with OK.
New Outlook and Outlook on the web
Open Settings (gear) › Accounts or Mail › Automatic replies.
Turn on Automatic replies, optionally set a time range.
Enter texts for internal and external senders and click Save.
Outlook for Mac
In the menu bar, choose Tools › Automatic Replies.
Turn it on, set time range and text, and confirm with OK.
Outlook app (iPhone and Android)
Tap your profile picture › gear and select your company account.
Open Automatic replies, turn it on, enter the text and save.
Tip: Name a substitute with contact details, e.g. “I'm out of the office until 14 Nov. For urgent matters, please contact office@company.com.” For shared mailboxes, see “Set up an automatic reply for a shared mailbox – Outlook”.