Thomson Reuters Hosted Exchange Retires August 31 — What CS Professional Suite Firms Must Do Now
Thomson Reuters retires Hosted Exchange for Virtual Office CS and Software-as-a-Service environments on August 31, 2026. Mailboxes not migrated by that date are scheduled to be permanently deleted. Virtual Office CS itself continues — UltraTax CS, Practice CS, Accounting CS and FileCabinet CS are unaffected — but email and Microsoft licensing move from Thomson Reuters’ responsibility to the firm’s.
For thousands of accounting practices, that is a quiet but significant shift in who owns a critical piece of the technology stack.
What is actually changing
Thomson Reuters has confirmed in its own support documentation that it will no longer host or support Exchange email for Virtual Office CS and SaaS firms after August 31, 2026. The company stopped creating new email domains in those environments earlier this year.
From that date, each firm must:
- Hold its own supported Microsoft 365 licenses
- Own and administer its own Microsoft 365 tenant
- Manage mailbox administration, spam filtering, retention policies and the DNS records that keep mail flowing
Thomson Reuters continues to host the Microsoft Office applications inside Virtual Office CS. What ends is the managed email service behind them.
Why this lands harder on small and mid-sized firms
A 60-person firm with an internal IT director absorbs a change like this. A 12-person practice where the managing partner is the IT department does not.
Email administration is not a one-time task. It is a standing responsibility: license renewals, mailbox provisioning when staff join, retention configuration, DNS records that silently break mail delivery when they drift, and spam filtering that has to be tuned rather than assumed.
There is a regulatory dimension too. For tax preparers, email is where client financial data lives. IRS Publication 4557 sets out safeguarding expectations for taxpayer data, and the FTC Safeguards Rule applies to tax preparers as financial institutions. A mailbox environment that nobody is clearly accountable for is a gap that a cyber insurer or a peer reviewer will eventually ask about.
The deadline is not the whole story
The more consequential question is not “who runs our email in September” but “how many vendors does this firm now depend on?”
Many practices already run a split stack: the CS Professional Suite in one environment, QuickBooks Enterprise on an office server or with a second host, add-ons somewhere else again. The Hosted Exchange retirement adds a Microsoft tenant to that list — and with it another login, another renewal date, and another vendor to call when something breaks across the seam between two systems.
That seam is where firms lose time in March. When UltraTax is with one provider and QuickBooks is with another, neither vendor owns a problem that spans both.
What a consolidated alternative looks like
Some firms are treating the deadline as the moment to reduce vendor count rather than increase it. Rather than adding a Microsoft tenant to an existing split, they move the whole stack into one managed environment.
OneUp Networks, a US-based managed cloud hosting provider focused on accounting and tax firms, is one of the providers positioned for this transition. Its model is a single dedicated environment — not a shared server — running the applications a firm already licenses: the Thomson Reuters CS suite, QuickBooks Desktop editions, CCH ProSystem fx, Sage, Drake, Lacerte, ProSeries, ATX, TaxWise, Microsoft applications and add-ons, reached through one login.
Two details matter for firms making a decision under deadline pressure. Migration is guided and phased, with the firm choosing its own cutover date and busy season avoided where possible — not a weekend switch-off. And support comes from engineers who work with tax and accounting software daily, available around the clock, rather than a first-tier script.
The company is not a software vendor and does not sell licenses. Firms keep or purchase their own Microsoft 365, UltraTax CS or QuickBooks licenses from the publisher; the hosting provider runs the environment those licensed applications live in.
What firms should do this week
| Action | Why it can’t wait |
|---|---|
| Confirm Microsoft 365 licenses are in place | Office applications inside Virtual Office CS are disrupted without a supported license |
| Verify every mailbox has been migrated | Remaining mailboxes are scheduled for permanent deletion after August 31 |
| Assign an owner for the M365 tenant | Tenant administration, DNS and retention are now the firm’s responsibility |
| Document the arrangement | FTC Safeguards §314.4(f) requires firms to oversee their service providers |
| Decide whether to consolidate | Adding a vendor and reducing vendors are both available options right now |
FAQ
Is Virtual Office CS being discontinued? No. Virtual Office CS continues. UltraTax CS, Practice CS, Accounting CS, Fixed Assets CS and FileCabinet CS operate as before. Only the Thomson Reuters–managed Hosted Exchange email service is retiring.
What happens to mailboxes that aren’t migrated by August 31, 2026? Thomson Reuters has stated that remaining Hosted Exchange mailboxes will be securely deleted when the service sunsets.
Does a firm need its own Microsoft 365 license now? Yes. A supported Microsoft 365 license is required to use Office applications and their integration with Thomson Reuters applications inside the environment.
Can a firm move its whole application stack to a single host instead? Yes. Providers such as OneUp Networks host the CS Professional Suite alongside QuickBooks, Microsoft applications and add-ons in one dedicated environment, so the firm manages one vendor rather than several.
Firms evaluating their options after the August 31 deadline can review published per-user plans and request a migration consultation at oneupnetworks.com, or call +1-888-657-0210.