A client currently operates two legally separate companies in the same building. They share the same physical network, file and Active Directory server, and Microsoft 365 tenant, with both email domains hosted together. Historically, they were treated as one IT environment under a single service agreement.
Now Company A is being transferred to the owner's son and no longer wants a service contract, while Company B will remain with the current owner and wants continued support. Since the companies still depend on the same network, servers, identities, and cloud tenant, supporting only Company B seems likely to create unclear responsibility, security concerns, and liability if something affecting Company A impacts the shared environment.
Would you continue supporting Company B under these conditions, require both companies to sign an agreement, or insist that the companies fund a complete separation of their network and Microsoft 365 environments first?
4 Answers
I would treat them as one IT environment until the separation is complete. Splitting a network is manageable, but separating Active Directory, shared data, mailboxes, identities, and the Microsoft 365 tenant is a real migration project. Supporting only one side of a shared environment creates a responsibility gap that is difficult to defend.
This is technically possible to co-manage, but it tends to become slow and contentious. The companies need a signed separation plan covering the network, tenant, domains, data, legacy systems, internet service, hardware, licensing, backups, and support boundaries. If they cannot agree on those basics, walking away may be safer than becoming responsible for the fallout.
Make the separation part of the commercial agreement. Company B can pay for the migration and infrastructure changes, then you can support Company B once it has its own clearly defined environment. Otherwise Company A could continue benefiting from Company B's contract while leaving you responsible for systems you are not being paid to manage.
My preference would be that both companies remain covered by one agreement, with the owners documenting who pays, who owns the equipment and data, and who is authorized to make decisions. If Company A refuses, I would either charge separate emergency rates for any work involving it or stop supporting the shared environment until the companies are separated.
Make sure the ownership and access arrangements are written down and reviewed by legal counsel. Questions about hardware, historical data, mailbox contents, backups, and administrator credentials can become very expensive once the business relationship deteriorates.
The Microsoft 365 divestiture should probably be handled by someone experienced with tenant migrations. It can be done, but the planning and data ownership issues make it much more complicated than simply creating another domain.