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.

The command you tried to run isn’t currently allowed in your organization. To run this command, you first need to run the command: Enable-OrganizationCustomization

When trying to add an anti-spam policy in O365 Security Portal the following message occurs: All the customers where we already added anti-spam policies without this message used Azure AD Connect, I think this activates the OrganizationCustomization option. On Windows 10, open elevated Powershell: Install-Module -Name ExchangeOnlineManagement Import-Module ExchangeOnlineManagement Connect-ExchangeOnline -UserPrincipalName user@domain.tld Enable-OrganizationCustomization