How do you remove certain mailboxes from the All Users Dynamic Distribution Group?

[Chris House]

We have the 'All Users' Dynamic distribution group within our Office 365 system and this includes as part of the Membership settings "Users with Exchange mailboxes".

I need to remove two mailboxes from this group however when I click on the "add a rule" button it just gives me a selection of attributes (state, company, department, custom attribute 1 and so on). It doesn't let me exclude mailboxes based on the user.

Does anyone know if it is possible to remove certain users from a dynamic group?

We don't have our Office 365 Business Essentials system linked to Active Directory.

Thanks in advance.

[#2]

Rules for DDG membership are indeed based on attributes, so you cannot just "point" to a given mailbox. An easy solution is to populate one of the customattributeXX values and use this as exception. You can create a more complex rules via PowerShell and the Set-DynamicDistributionGroup cmdlet, such as excluding certain mailboxes by Name, DisplayName, GivenName, whatever other attribute you can think of...