Your Admin can Grant access to one mailbox from another.
This is known as mailbox delegation. You need to be a licensed user to be delegated access to another mailbox but once done you don’t need to have passwords or other credentials since the whole thing relies on your credentials for permission.
Most commonly this is done for a shared mailbox like orders@yourcompany.com or perhaps another staff member who may be on leave.
Best practice is not to “map” the other mailbox to your Outlook desktop app.
Automapping to Desktop Apps
When delegating a mailbox to another user we choose to Automap or not to Automap the delegation.
If Automapping is OFF (or false) when the mailbox is delegated then the mailbox must be accessed via Webmail.
If Automapping is ON (or true) when the mailbox is delegated then the mailbox WILL appear connected to the Outlook Desktop App on Windows (not so for Mac unless something changes) and can also be accessed via Webmail.
Opening a Delegated Mailbox in Webmail
Often the most convenient and certainly the fastest way to search a mailbox is via Outlook Web Access (OWA).
Use this link to open your webmail: https://outlook.cloud.microsoft/
Just click your name or initials in the top right hand corner of our Outlook Web Mail and then choose “open another mailbox”.
In the Open another mailbox dialog just start typing the name of the shared mailbox, office will auto prompt so you can select it from a list.
When you see it click on it and it will open in a new tab right in your browser (provided you have been delegated permissions to the mailbox).
Microsoft’s take on exposing the Automapping status for mailboxes
In Exchange Online, the Automapping setting for shared and delegated mailboxes is implemented as part of the Autodiscover service logic rather than as a persistent, reportable permission attribute.
While the automapping decision is stored internally to ensure consistent client behaviour across devices and profiles, it is intentionally not exposed through administrative interfaces, PowerShell, Microsoft Graph, or reporting APIs. This design reflects Automapping’s role as a client experience optimisation rather than a security, compliance, or access control boundary. As a result, administrators can control Automapping only at the time permissions are assigned, but cannot retrospectively query or audit this setting. This behaviour is by design and aligns with Microsoft’s service abstraction model, where internal directory metadata required for service operation is not surfaced unless it represents a supported management or compliance signal.
Changing Automapping for a mailbox: To change the Automapping for a mailbox means removing the delegation and redelegating it again choosing the appropriate Automapping parameter.