question

Hi @DanielKlobnak-9307

I have tried this in my environment, if we click the button in outlook client, it will open the browser and open the OWA page, please make sure you login the o365 account on the browser, then it will go to the right page. If you haven't login the account on the browser, it will suggest you create a new account. That's the expected behavior.

Since the feature is exclusively web-based. We can directly click the button through OWA, then it can show the shared calendar page.

In addition, if you want to share free-busy between o365 tenants, you may also consider creating an organization relationship between them. Like this similar thread discussed: How to Share Room Calendars Externally in Office 365?

And the official document here for your reference as well: Create an organization relationship in Exchange Online

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Thank you for the information. I will be testing further tomorrow. My results were similar when I clicked on the links from within OWA as well ( I am not sure if there may some impact based on 3rd party AV on my side). I do have a number of different tenants available to review against.

I did review the organizational relationships option, however this particular client likely has a much wider audience than a few domains as there are several hundred independent contractors and partners (including many who have free email accounts).

Again, thank you for the feedback. I will update appropriately.

Hi, the challenge was resolved. Frankly, the process does not necessarily work as directly as most documentation indicates. It is generally missing a step (and part of it is the way I have some items set up).

Basically once the share request is received, and one opens in OWA, one is redirected to outlook.live.com.
However, as I did not have an Outlook.live account I did not select the "Sign In".
Had I, and entered my 365 Creds, I likely would have been fine.
I discovered this, as I inadvertently selected Yes when prompted if "I always want to stay signed on" to minimize the times I am asked to enter creds. Normally I always say No (as I enter numerous portals etc. for various customers).
When I selected yes to 'always stay signed on', then accepted the Share, Outlook.live came up but then I was redirected back to OWA and the calendar worked as advertised.
(It's a minor detail to be sure, but it was a missing piece to the documentation - and when I reference detailed documentation I anticipate no missing pieces - but most folks likely "always stay signed on" (yikes).

As the custromer's partner is using a different email platform, I went through the whole process again with a gmail account. This time I created an Outlook.live account, and all worked.

The only thought/question which I have not tested yet - if I share a calendar with Yahoo@gmail.com and Yahoo@gmail.com creates a Yahoo@outlook.com account to access the calendar successfully, if I later stop the share with Yahoo@gmail.com will Yahoo@outlook.com account no longer have access?