On the navigation bar, choose Settings > Automatic replies.
Choose the Send automatic replies option.
Select the Send replies only during this time period check box, and then enter a start and end time to control when automatic replies are sent.
If you don't set a time period, your automatic reply remains on until you turn it off by selecting Don't send automatic replies.
Select the check box for any of the following options that you're interested in:
Block my calendar for this period
Automatically decline new invitations for events that occur during this period
Decline and cancel my meetings during this period
If you want senders outside your organization to get automatic replies, select the check box for Send automatic reply messages to senders outside my organization.
In the box at the bottom of the window, type a message to send to people during the time you're away.
If you like, you can highlight your message and use the formatting options at the top of the box to change the font and color of the text, add an emoji, or customize your message in other ways.
When you're done, choose OK at the top of the page to save.
If you didn't set a time period for automatic replies (step 4 earlier), you'll need to turn them off manually.
To turn off automatic replies, sign in to Outlook on the web, choose Settings > Automatic replies and then select Don’t send automatic replies.