Microsoft 365 inter-tenant collaboration

Suppose that two organizations, Fabrikam and Contoso, each have a Microsoft 365 for business tenant and they want to work together on several projects; some of which run for a limited time and some of which are ongoing. How can Fabrikam and Contoso enable their people and teams to collaborate more effectively across their different Microsoft 365 tenants in a secure manner? Microsoft 365, in conjunction with Azure Active Directory (Azure AD) B2B collaboration, provides several options. This article describes several key scenarios that Fabrikam and Contoso can consider.

Microsoft 365 inter-tenant collaboration options include using a central location for files and conversations, sharing calendars, using IM, audio/video calls for communication, and securing access to resources and applications. Use the following tables to select solutions and learn more.

Exchange Online collaboration options

Sharing goal Administrative action How-to information
Share calendars with another Microsoft 365 organization Administrators can set up different levels of calendar access in Exchange Online to allow businesses to collaborate with other businesses and to let users share the schedules (free/busy information) with others.
Control how users share their calendars with people outside your organization Administrators apply sharing policies to users mailboxes to control who it can be shared with and the level of access granted
Configure secure email channels and control mail flow with partner organizations Administrators create connectors to apply security to mail exchanges with a partner organization or service provider. The connectors enforce encryption via transport layer security (TLS) as well as allowing restrictions on domain names or IP address ranges your partners send email from.

SharePoint Online and OneDrive for Business collaboration options

Sharing goals Administrative action How-to information
Share sites and documents with external users Administrators configure sharing at the tenant, or site collection level for Microsoft account authenticated, work or school account authenticated or guest accounts
Tracking and controlling external sharing for end users OneDrive for Business file owners and SharePoint Online end users configure site and document sharing and establish notifications to track sharing

Skype for Business collaboration options

Sharing goal Administrative action How-to information
Skype for Business Online - IM, calls, and presence with other Skype for Business users Administrators can enable their Skype for Business Online users to IM, make audio/video calls, and see presence with users in another Microsoft 365 tenant. Allow users to contact external Skype for Business users
Skype for Business Online - IM, calls, and presence with Skype (consumer) users Administrators can enable their Skype for Business Online users to IM, make calls, and see presence with Skype (consumer) users. Let Skype for Business users add Skype contacts

Azure AD B2B Collaboration options

Sharing goal Administrative action How-to information
Azure AD B2B collaboration - Content sharing by adding external users to a group in an organization's directory A global admin for one Microsoft 365 tenant can invite people in another Microsoft 365 tenant to join their directory, add those external users to a group, and grant access to content, such as SharePoint sites and libraries for the group.

Microsoft 365 collaboration options

Sharing goal Administrative action How-to information
Microsoft 365 Groups - Email, calendar, OneNote, and shared files in a central place Groups are supported in Business Essentials, Business Premium, Education, and the Enterprise E1, E3, and E5 plans. People in one Microsoft 365 tenant can create a group and invite people in another Microsoft 365 tenant as guest users. Applies to Dynamics CRM as well.

Yammer collaboration options

Sharing goal Administrative action How-to information
Yammer - Collaboration through an enterprise social medium Unless the ability to create external groups is disabled by a Yammer admin, users can create external groups to collaborate in Yammer through conversations, the ability to like and follow posts, share files, and chat online. Create and manage external groups in Yammer

Teams collaboration options

Sharing goal Administrative action How-to information
Collaborate in Teams with users external to the organization A global admin for the inviting Microsoft 365 tenant needs to enable external collaboration in Teams. Global admins and team owners will now be able to invite anyone with an email address to collaborate in Teams.
Admins can also manage and edit Guests already present in their tenant.
Team owners can invite and manage how guests collaborate within their teams. Team owners have additional controls on what the guests can do within their teams.
Guests from other tenants can view contents in Teams and collaborate with other members None. The guest access experience

Power BI collaboration options

Sharing goal Administrative action How-to information
Power BI enables external guest users to consume content shared to them through links. This enables users in the organization to distribute content in a secure way across organizations.
The Power BI Admin can control whether users can invite external users to view content within the organization. Distribute Power BI content to external guest users with Azure AD B2B

Points to be aware of about Microsoft 365 inter-tenant collaboration

Sharing of user accounts, licenses, subscriptions, and storage

Each organization maintains its own user accounts, identities, security groups, subscriptions, licenses, and storage. People use the collaboration features in Microsoft 365 together with sharing policies and security settings to provide access to needed information while maintaining control of company assets.

  • User accounts: Accounts cannot be shared or duplicated between the tenants or partitions in the on-premises Active Directory Domain Services.

  • Licenses & subscriptions: In Microsoft 365, licenses from licensing plans (also called SKUs or Microsoft 365 plans) give users access to the Microsoft 365 services that are defined for those plans.

  • Storage: In Microsoft 365 licensing plans, software boundaries and limits for SharePoint Online are managed separately from mailbox storage limits. Mailbox storage limits are set up and managed by using Exchange Online. In both scenarios, storage can't be shared across tenants.

Can we share domain namespaces across Microsoft 365 tenants?

No. Organization domain names, such as fabrikam.com or tailspintoys.com, can only be associated and used with a single Microsoft 365 tenant. Each tenant must have its own namespace. UPN, SMTP, and SIP namespaces cannot be shared across tenants.

What about hybrid components and Microsoft 365 inter-tenant collaboration?

On-premises hybrid components, such as an Exchange organization and Azure AD Connect, cannot be split across multiple tenants.