Dutch Tax Agency Moves Its Mail Off Microsoft 365

A Cloud Migration Reversed Within A Year

The Netherlands Tax and Customs Administration told parliament this week that it will not complete its Microsoft 365 migration. It will run mail and calendar on infrastructure it controls from 2027, followed by European open-source tools for storage and collaboration in late 2027 and 2028, according to a letter from State Secretary for Finance Eelco Eerenberg.

About 5,000 of the roughly 47,000 employees had already moved when the rollout stopped, so this is a partial reversal of a programme running since 2021.

What The Advisory Board Found

The Adviescollege ICT-toetsing (AcICT) called the public-cloud design unsuitable in a report that reached the tax office in the summer. It said sensitive documents in the collaboration environment travelled via US servers, that standard Microsoft encryption was used instead of Double Key Encryption, and that end-to-end encryption in Teams was off by default.

The sharpest findings were about recovery. Data, backups and archives all sat in the same single-vendor cloud, files that crashed or were encrypted could not be restored outside Microsoft 365, and in basic tests the backup software failed on empty folders. The board also found no substantiated business case and no workable exit strategy.

The Register points out that many of these concerns come from how the tax office configured Microsoft 365 rather than from the product itself. That is the point worth keeping: the reversal says more about migration discipline than about a vendor.

The Price Of Autonomy Is Paid In Schedule

The letter gives one reason the on-premises route is possible now. The tax office has managed to expand its datacentre capacity. In February a hybrid on-premises Exchange option had been judged technically infeasible, so the change is partly a change in what the agency can host.

It also names costs. The new approach reuses existing licences to limit extra spending, but some planned records-management features sat inside the Microsoft package and are not available on-premises, and the agency is still working out how to replace them. In a separate project, taking over a supplier's hosting of the new VAT system for reasons of digital autonomy pushed the VAT-refund go-live to April 2027 and moved domestic VAT rollout from 1 July 2027 to the third quarter of 2027.

Early European sovereign deployments report friction too. Politico reported harsh internal reviews of a Microsoft Teams backup that the European Commission rolled out on its own infrastructure. Autonomy is available, and it arrives with a delivery date attached.

What To Do If One Vendor Runs Your Office

Test a restore without the vendor's own tools. Delete a folder, corrupt a file and bring it back from a copy the vendor cannot reach. If you cannot do that today, you have found the Dutch tax office's problem in your own tenant.

Write and price the exit plan before the migration, not after it. List how long it would take, which licences you could reuse and which features would disappear. The AcICT advice was to examine alternatives per function instead of assuming one suite from one supplier.

Keep a list of what exists only inside the suite, such as records management, e-discovery or compliance labels, because that list becomes your cost the day you leave.

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Read next: Microsoft Raises 365 Prices as France and German States Walk Away  |  Ireland Cancels Its EUR1 Billion Microsoft Tender