Are you asking how to add a trusted mailbox to office365? Add a trusted mailbox through the security and compliance settings in the settings.

1. Log in to the Office 365 account, click the "Settings" icon in the upper right corner of the page, select the "Options" menu, and then select the "Security and Compliance" option.

2. In the "Security and Compliance" setting interface, click the "Security and Compliance Center" link.

3. In the pop-up "Add Sender" or "Add Domain" dialog box, enter or select the trusted mailbox or domain name to be added, and complete the addition.