Step 1: In Chrome, go to outlook.office.com and sign in with your normal email account.
Step 2: Click your profile picture in the top right corner, then choose Open another mailbox.
Step 3: Type the name of the mailbox(if it is [email protected] just put in example as the mailbox name) and select it, then click Open. It will open in a new browser tab.
Step 4: In that new tab, click the gear icon in the top right, then go to Accounts > Automatic replies.
Step 5: Turn automatic replies on, enter your message, and save.