A shared mailbox (e.g. office@company.com) can also reply automatically, for example during a company holiday. This is easiest in Outlook on the web. Requirement: full access to the shared mailbox.
Steps
Open outlook.office.com and sign in with your own company account.
Click your profile picture in the top right and choose Open another mailbox.
Enter the address of the shared mailbox and click Open. The mailbox opens in a new tab.
In this tab, go to Settings (gear) › Mail › Automatic replies.
Turn on Automatic replies, optionally set a time range, and enter the texts for internal and external senders.
Click Save.
Important: The setting must be made in the shared mailbox's tab. Otherwise it applies to your own mailbox.
Note: If the mailbox can't be opened, full access is missing. Please contact support.