There are automatic (out-of-office) replies which can be set on a schedule but perhaps you want to forward email to another user when you're away on holiday. Forwarding can be done by the user.
Alternatively, ask your Office 365 admin to give another user access to the shared mailbox.
Do the following before going away. When you return from holiday, follow the same instructions but for the last step, choose option Stop forwarding.
Login to your Office 365 mailbox, go to https://outlook.office365.com and login with your username and password.
Once you are logged in, click on the top right of the screen where your user picture is located and select Open another mailbox.
A popup will appear on the screen where you can enter the name of the shared mailbox.
Click search directory and Office 365 will search for matching names.
Select the name required and click open. A new window will open for the shared mailbox.
The next step is to click on the cog again, this is located in the top right of the screen. Then select Mail.
Select Mail > Accounts > Forwarding. Choose option Start Forwarding.
Then fill in email address to receive forwarded email. Click Save.