Office 365 inter-tenant collaboration

This article describes several ways to collaborate between two Office 365 tenants. It is intended for Office 365 Administrators.

Suppose that two organizations, Fabrikam and Contoso, each have an Office 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 Office 365 tenants in a secure manner? Office 365, in conjunction with Azure Active Directory B2B collaboration, provides several options. This article describes several key scenarios that Fabrikam and Contoso can consider.

Office 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 Office 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
Sharing in Exchange Online
Organization relationships in Exchange Online
Create an organization relationship in Exchange Online
Modify and organization relationship in Exchange Online
Remove an organization relationship in Exchange Online
Share calendars with external users
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
Sharing policies in Exchange Online
Create a sharing policy in Exchange Online
Apply a sharing policy to mailboxes in Exchange Online
Modify, disable, or remove a sharing policy in Exchange Online
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.
How Exchange Online uses TLS to secure email connections in Office 365
Configure mail flow using connectors in Office 365
Remote domains in Exchange Online
Set up connector for secure mail flow with a partner organization
Mail flow best practices for Exchange Online and Office 365 (overview)

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
Manage external sharing for your SharePoint Online environment
Restricted Domains Sharing in Office 365 SharePoint Online and OneDrive for Business
Use SharePoint Online as a business-to-business (B2B) extranet solution
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
Configure notifications for external sharing for OneDrive for Business
Share SharePoint files or folders in Office 365

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 Office 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 Office 365 tenant can invite people in another Office 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.
What is Azure AD B2B collaboration preview?
Azure AD B2B: New updates make cross-business collab easy
Office 365 external sharing and Azure Active Directory B2B collaboration
Azure Active Directory B2B collaboration API and customization
Azure AD and Identity Show: Azure AD B2B Collaboration (Business to Business

Office 365 collaboration options

Sharing goal Administrative action How-to information
Office 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 Office 365 tenant can create a group and invite people in another Office 365 tenant as guest users. Applies to Dynamics CRM as well.
Learn about Office 365 groups
Guest access in Office 365 Groups
Deploy Office 365 Groups

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 Office 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.
Authorize Guest Access
Turn Guest Access On or Off in Teams
Use PowerShell to control Guest Access
Guest Access Checklist
View Guest Users
Edit guest user information
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.
Add Guests
Add a guest to a team
Manage Guest Access in Teams
See who's on a Team or in a Channel
Guests from other tenants can view contents in Teams and collaborate with other members
None.
The guest access experience

Points to be aware of about Office 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 Office 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 and accounts cannot be duplicated between the tenants or partitions in the on-premises Active Directory Directory Services.

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

  • Storage: In Office 365 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 cross tenants.

Can we share domain namespaces across Office 365 tenants?

No. Vanity domains, such as fabrikam.com or tailspintoys.com, can only be associated and used with one tenant at the time. Each tenant must have its own namespace; UPN, SMTP and SIP namespaces cannot be shared across tenants.

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

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