Hide a Mail-Enabled User from the Global Address List

In an Exchange hybrid environment, change recipient visibility using the system that is authoritative for Exchange attributes. If the object is synchronised from on-premises Active Directory, make the change with supported on-premises Exchange tools and let directory synchronisation carry it to Microsoft 365.

Exchange Management Shell example

Set-RemoteMailbox -Identity [email protected] \
  -HiddenFromAddressListsEnabled $true

For an on-premises mailbox, use the corresponding Set-Mailbox command.

Verify

Get-RemoteMailbox -Identity [email protected] |
  Select-Object DisplayName,HiddenFromAddressListsEnabled

After synchronisation and address-book processing, confirm the recipient no longer appears where expected. Hiding an object from address lists does not disable sign-in, mail delivery or mailbox access; apply separate controls if those are also required.