Shared accounts/ mailboxes are accessible to more than one user, and can be used for a specific project, task, or department. Access to a shared account can be set up either by:
...
A security group, where a user with permission for the account can their own credentials to access the account.
...
requested by submitting a request to ETIS.
Please see below for instructions on how to access the shared mailbox
Adding a shared mailbox to Outlook (Classic)
...