Yes, Quest and Proofpoint are two solutions that I’m aware of, both of which utilize matching between source and target accounts to rewrite message headers, described at a high-level in the following article – https://practical365.com/using-email-address-rewrite-to-alleviate-domain-sharing-challenges/.

I don’t have details regarding Proofpoint’s solution, but I’ve talked to a few existing Proofpoint customers that used it successfully. Quest has a standalone product called ODM Domain Rewrite that is used by many companies, which you can find more info about on Quest’s website – https://www.quest.com/products/on-demand-migration/domain-rewrite.aspx

Are there any 3rd party tools that could help with cross tenant sharing of email domain names? Quest? Proofpoint?

Jakke, it is not on any upcoming roadmaps, but I imagine that Microsoft is still considering it, since it remains a highly desired feature and they have been releasing many other features to support multi-tenant organizations.

As Portwajn suggested below, you should consider it off the table for now and look into third-party Domain Rewrite solutions to meet any immediate or upcoming needs. Perhaps we will see a native solution preview again in a few years.

This is what I call “the arrogance of power” – but also “Pride comes before a fall”.

In our case – a merger of a dozen smaller companies into a holding with 1.500 employees – we decided to switch to slack business. Exactly because Microsoft is so obviously indifferent to the needs of its customers.

Correct – the item was now completely removed from the roadmap.