Remote Server returned ‘550 5.7.520 Access denied, Your organization does not allow external forwarding. Please contact your administrator for further assistance. AS(7555)’

When trying to use external forwarding on a Shared Mailbox: user@domain.tldRemote Server returned ‘550 5.7.520 Access denied, Your organization does not allow external forwarding. Please contact your administrator for further assistance. AS(7555)’ Go to: https://protection.office.com/antispam Create policy -> Outbound -> user@domain.tld -> Forwarding is enabled.