Hi Mark,
I’d like to confirm your needs:
Your client want to share their personal contacts with the same domain. However, they don’t want users in the same Office 365 organization but under different domain to see these contacts, because they are from separate business departments.
If I have misunderstood you, please don’t hesitate to correct me.
As for the shared contacts feature for OWA, you are right. This is not available in Office 365 at present. You can submit feedback to let our product team know your needs. Many feature are designed and updated according to customers’ advices.
And for the shared contacts issue in Outlook, could you please describe it in more details so that I can understand the issue better? What do you mean by “use it as an address book” and “can’t edit one list”? Your time and effort are highly appreciated.
Best Regards,
Henry Huang