Exchange Online (Office 365) - Hide from Exchange address lists.
Using this feature, you can hide the desired users' mailboxes from the Exchange address lists.
- Click the Management tab.
- Select Office 365 Management in the left pane. Then click the hide from address lists link located under Mailbox Management.
- Select the desired Office 365 account.
- Select the desired users from the list.
- Click the Configure link located at the right extreme.
- In the hide from Exchange address lists field, select Yes or No, as needed.
- Click Apply.