Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Hi Info,
If you want to access other people’s mailbox, please contact your Office 365 admin add your account to the mailbox delegation list of that mailbox. Navigate to Exchange Admin Center(EAC) -> Recipients -> Mailbox, click and edit the mailbox. Choose Mailbox Delegation, add your mailbox to the different permission lists. If you want to delegate a shared mailbox, please navigate to EAC -> recipients -> shared, click and edit the shared mailbox. You can see this article for reference: Accessing other people’s mailboxes in Office 365
If you have any questions about it, please feel free to contact us.
Best regards,
Rick