Migrating Off IONOS: Choosing Microsoft 365 and Setting Up Single Sign-On
The client's email had been sitting on IONOS for years, and it had quietly become a limitation. The bigger decision wasn't the migration itself, it was which platform to land on, and what that platform would let them do next.
IONOS had worked fine as a starting point years ago: cheap domain registration, basic email hosting, nothing fancy. But as the business grew, the limits started showing. Mailbox management was clunky, there was no real identity system behind it, no MFA enforcement worth trusting, and every new hire or offboarding was a manual, error-prone process. The email itself still worked. What it couldn't do anymore was serve as the foundation for the rest of the business's IT.
The real question wasn't email, it was identity
Once we started scoping the migration, the conversation quickly became less about "where does mail live" and more about "what system manages who has access to what." The client also runs a piece of custom line-of-business software that, at the time, required its own separate login, one more password for staff to manage and one more account for IT to provision and deprovision by hand. Whichever platform we migrated email to was also going to become the identity backbone for everything else, so the decision deserved real scrutiny instead of a coin flip.
Whichever platform we migrated email to was also going to become the identity backbone for everything else.
Google Workspace vs. Microsoft 365, for this business specifically
We walked the client through both options honestly. Google Workspace would have worked, and for a lot of businesses it's the right call. But two things tipped this one toward Microsoft 365: their staff had spent years working in Word and Excel and already knew the ecosystem cold, and their custom software's authentication options integrated far more cleanly with Microsoft Entra ID than with Google's identity platform. Familiarity plus a cleaner integration path made this a fairly one-sided decision once we actually dug into it, even though it wasn't obvious at the outset.
We covered the general version of this decision, features aside, in more depth in our Office 365 vs. Google Workspace write-up. This client is a good example of exactly the pattern described there: the platforms are close enough on paper that the deciding factors end up being team habits and what your other software expects, not a feature checklist.
The migration itself
We moved the domain and every mailbox from IONOS to Microsoft 365 with mail flow kept intact the whole time, no bounced messages, no missed client emails during the cutover. MFA went on every account as part of the same project, not as a follow-up nobody gets around to.
Single sign-on for their custom software
With Microsoft 365 as the identity provider, we configured single sign-on for the client's custom software so staff log in once with their Microsoft 365 credentials instead of juggling a second, separate password. That also meant offboarding got simpler: disable one account in Microsoft 365 and access to the custom software goes with it, instead of someone having to remember there's a second system to lock down.
The net result: one login for staff, one place for us to manage access, and MFA that actually covers the software that matters most to this business, not just email.