Welcome to sharing and organization relationships in Exchange Online. In this lesson, we'll take a look at the different options that are available for configuring, for sharing between organizations in Exchange Online. In most production environments, you're going to have to offer the ability for users in one organization to coordinate scheduling with users and another organization, that's just how business is conducted. Microsoft 365 offers you the ability to configure different levels of calendar access in Exchange Online so that this type of collaboration can occur. In other words, it allows you to permit users to share their calendars with others. There's a few different sharing scenarios that Exchange Online supports. More specifically, it supports the sharing of calendars with other Microsoft 365 organizations. It supports sharing calendars with an on-prem Exchange organization and it supports sharing Microsoft 365 user calendars with other Internet users as well as with Exchange on-prem users.

To facilitate the sharing of calendars with other Microsoft 365 organizations, you configure organization relationships which are one-to-one relationships between businesses. When you configure an organization relationship, it allows users in each organization in the relationship to view calendar availability information for each other. Aside from configuring an organization relationship, there's really nothing else to configure to allow the sharing of calendars with other Microsoft 365 organizations. Sharing calendars with an on-prem Exchange organization also requires you to set up an organization relationship. 

However, to facilitate this kind of sharing, you also have to ensure that the on-prem Exchange admin sets up an authentication relationship or federation with the Cloud. To facilitate the sharing of a Microsoft 365 users calendar with another Internet user, you use sharing policies. You also use sharing policies to facilitate the sharing of Microsoft 365 user calendars with Exchange on-prem users. You also have to ensure in this case that the on-prem Exchange admin sets up federation with the Cloud. Ultimately, what you want to do to facilitate business-to-business calendar sharing is create Organization Relationships. If you need to set up user-to-user calendar sharing, you use Sharing Policies.

I should also mention that you can specify three levels of access to your organization information when configuring sharing: You have no access, you have access to availability which is free/busy time only and you have access to free/busy including time, subject and location. Users that prefer to not share their free/busy information with others can simply change their permissions in Outlook. This is done by opening Outlook, going to calendar properties and then onto the permissions tab where they can choose users and groups and set their preferred permissions options. So, really the key takeaway for this lesson is that organization relationships are typically used to facilitate business-to-business calendar sharing and Sharing Policies are typically used to set up user-to-user calendar sharing.