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Key Microsoft 365 Inter-Tenant Collaboration Options

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AmyKelly Petruzzella
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Two organizations each have Microsoft 365 tenants 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 these organizations enable their people and teams to collaborate more effectively and productively across their different tenants? Add on top of this, how can this be done in a secure and compliant manner? This article describes several key collaboration options that administrators at each organization can consider as shared goals.

Exchange Online collaboration options

  • GOAL: Share calendars with another Microsoft 365 organization
    • ADMIN ACTION: 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.
  • GOAL: Control how users share their calendars with people outside your organization
    • ADMIN ACTION: Administrators apply sharing policies to users mailboxes to control who it can be shared with and the level of access granted
  • GOAL: Configure secure email channels and control mail flow with partner organizations
    • ADMIN ACTION: 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

  • GOAL: Share sites and documents with external users
    • ADMIN ACTION: Administrators configure sharing at the tenant, or site collection level for Microsoft account authenticated, work or school account authenticated or guest accounts
  • GOAL: Tracking and controlling external sharing for end user
    • ADMIN ACTION: OneDrive for Business file owners and SharePoint Online end users configure site and document sharing and establish notifications to track sharing

Microsoft 365 collaboration options

  • GOAL: Microsoft 365 Groups - Email, calendar, OneNote, and shared files in a central place
    • ADMIN ACTION: 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.

Teams collaboration option

  • GOAL: Collaborate in Teams with users external to the organization
    • ADMIN ACTION: 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.
  • GOAL: Team owners can invite and manage how guests collaborate within their teams.
    • ADMIN ACTION: Team owners have additional controls on what the guests can do within their teams.
  • GOAL: Guests from other tenants can view contents in Teams and collaborate with other members
    • ADMIN ACTION: None.

FAQs about Microsoft 365 inter-tenant collaboration

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.

What exactly can be shared across 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 or, 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.


Microsoft collaboration apps efficiently and effectively support day-to-day work activities for employees, partners and vendors – which ever tenant they may reside in. It is crucial that Office 365 is available when needed, wherever needed, and across various teams internally and externally. Because today’s businesses are heavily reliant on technology, specifically Office 365, it becomes a significant barrier to end user productivity when (not if) systems fail. To get the most out of your collaboration platform, you can avoid top Office 365 admin challenges, by monitoring service availability and reviewing all back-end settings and policies to find the right balance between security and governance and employee productivity.

The Importance of Office 365 Monitoring

In a cloud-world, outages are bound to happen. While Microsoft is responsible for restoring service during outages, IT needs to take ownership of their environment and user experience. It is crucial to have greater visibility into business impacts during a service outage the moment it happens.

ENow’s Office 365 Monitoring and Reporting solution enables IT Pros to pinpoint the exact services effected and root cause of the issues an organization is experiencing during a service outage by providing:

  • The ability to monitor entire environments in one place with ENow’s OneLook dashboard which makes identifying a problem fast and easy without having to scramble through Twitter and the Service Health Dashboard looking for answers.
  • A full picture of all services and subset of services affected during an outage with ENow’s remote probes which covers several Office 365 apps and other cloud-based collaboration services.

Identify the scope of Office 365 service outage impacts and restore workplace productivity with ENow’s Office 365 Monitoring and Reporting solution. Access your free 14-day trial today!


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