Outlook 2003 or earlier versions don’t have this option.Īfter you set this key and restart Outlook, you’ll see the “+” sign is gone: HKCU\Software\Policies\Microsoft\Office\12.0\Outlook\Options\Mail\DisableDLExpansion=1 (REG_DWORD) HKCU\Software\Microsoft\Office\14.0\Outlook\Options\Mail\DisableDLExpansion=1 (REG_DWORD) HKCU\Software\Microsoft\Office\15.0\Outlook\Options\Mail\DisableDLExpansion=1 (REG_DWORD) What you could do is remove the option to expand the distribution group by setting one of the following a registry keys, depending on your Outlook client version: Fiddling around with the ACL sounds like a viable option (remove permissions to read members) but sounds like a potential cause for other issues so I wouldn’t recommend that.
Unfortunately, hiding isn’t a real option because distribution groups are universal distribution groups and its members are readable. Especially with moderated distribution groups this might be found an issue, because customers might want to hide membership information from senders. As you probably know, after entering a distribution group in the address bar, Outlook will show a “+” sign next to it which will let you replace the distribution group with all its members as recipients.
A customer was using moderated distribution groups and asked if it was possible to disable the expansion of distribution groups in Outlook.
