As of 6 Nov 2026, the panel rates Microsoft 365 Business 3/5 and Proton for Business 3.5/5 in Business Email & Office Suites. Weighted by what each judge cares about, 4 of the 6 judges pick Microsoft 365 Business and 2 pick Proton for Business. Microsoft 365 Business scores higher on 3 of 7 criteria (Calendar, contacts & office apps, Migration, open standards & exit and Mail, domains & deliverability). Proton for Business scores higher on 4 of 7 criteria (European sovereignty, Pricing transparency, Administration, identity & partner management, plus 1 more). Provenance — Microsoft 365 Business: Rest of world; Proton for Business: UK / wider Europe. Ratings are the AI panel’s opinion, formed from public evidence: how scores are made.
Microsoft 365 Business and Proton for Business split this bench. Microsoft 365 Business holds the productivity side: mail and deliverability at 7.0 vs 5.8 and calendar and office at 7.5 vs 6.2, six judges leaning its way on each, plus migration and portability at 7.0 vs 5.7, five judges to one. Proton for Business holds the governance side: security and compliance at 7.3 vs 6.5, where four judges lean Proton and two tie; administration and identity at 7.2 vs 6.3, five lean Proton and one tie; and sovereignty at 6.7 vs 4.5 plus pricing transparency at 7.0 vs 5.8, six judges leaning Proton on each. The weighted totals carry the split through: of five judges with totals shown, the IT administrator, IT service provider and skeptic put Microsoft 365 Business ahead, while the public-sector IT lead and data protection officer put Proton for Business ahead.
Choose Microsoft 365 Business if
You need the office suite itself — documents, spreadsheets and calendars — as the core of the purchase; calendar and office leans Microsoft 365 Business 7.5 to 6.2, six judges to zero.
Your mail operations depend on per-plan limits, quarantine and a hosted Exchange Online setup; mail and deliverability leans Microsoft 365 Business 7.0 to 5.8, six judges to zero.
Your team is moving mail into or out of the platform and wants a documented path both ways; migration and portability leans Microsoft 365 Business 7.0 to 5.7, five judges to one.
You buy the way the IT administrator, the IT service provider or the skeptic does; their weighted totals put Microsoft 365 Business ahead at 6.4 vs 6.3, 6.6 vs 6.4 and 6.5 vs 6.2.
Choose Proton for Business if
You need encryption the provider states it cannot decrypt, backed by ISO 27001 and SOC 2 Type II; security and compliance leans Proton for Business 7.3 to 6.5, four judges lean Proton and two tie.
Your team runs SAML sign-on with Okta or Microsoft Entra ID, three admin roles with a permission matrix, and a SCIM 2.0 API; administration and identity leans Proton for Business 7.2 to 6.3, five judges lean Proton and one tie.
Data sovereignty is your deciding criterion; it leans Proton for Business 6.7 to 4.5, six judges to zero.
You want the steadiest published pricing picture; pricing transparency leans Proton for Business 7.0 to 5.8, six judges to zero.
You buy the way the public-sector IT lead or the data protection officer does; their weighted totals put Proton for Business ahead at 5.9 vs 6.7 and 6.3 vs 7.1.
Read this comparison as one judge. Each weighs the same scores by what they care about.
The Small Firm Owner
Runs a tax and accounting firm of twelve in Lower Saxony. Every member of staff lives in Outlook, the shared "kanzlei@" mailbox is the busiest address in the office, and the meeting room is booked by shouting across the corridor. Wants mail on the firm's own domain that arrives, a shared calendar and address book on every phone, a move from the old provider that does not lose a single client thread, and a per-user price that is still the price in the second year.
Microsoft 365 Business
This judge's pick
Proton for Business
Criterion by criterion
Mail, domains & deliverability
Microsoft 365 Business
The mailbox side is strong for our firm: Exchange Online brings quarantine that admins and users manage, multi-engine anti-spam and anti-malware on all plans, Exchange ActiveSync policies for the phones, shared mailboxes with their stated sizes and licensing, out-of-office replies and server-side rules, and message, attachment and storage limits spelled out per client, with S/MIME signing and encryption available. For mail on our own domain, however, we found no public information on custom-domain DNS set-up, SPF, DKIM, DMARC, MTA-STS or DANE, catch-all or plus addressing, or the delivery reputation of the outbound infrastructure.
Proton for Business
Custom domains with catch-all, groups, SPF, DKIM with automatic 2048-bit key rotation every six months and DMARC are documented, with DNS set-up guides for a dozen registrars, and Bridge brings the mailbox into Outlook, Thunderbird and Apple Mail over IMAP and SMTP. We found no public information on native Outlook MAPI or ActiveSync, DMARC reporting, MTA-STS or DANE, plus addressing, delegated send-as or an admin-reviewable quarantine, and Bridge downloads all mail to each machine locally — not how I want twelve people on one busy mailbox. Mailbox and send limits beyond the per-user storage figures are also not documented.
Calendar, contacts & office apps
Microsoft 365 Business
This is the office our twelve people already live in: conference room management and calendar sharing, federated sharing with calendar publishing, the global address list and offline address book, Word, Excel, PowerPoint and Outlook for desktop, web and mobile, 1 TB of OneDrive per user, Teams and more than ten further apps in the bundle. Room-booking approval, delegated calendar access and co-editing in the browser are not spelled out on the pages we read, which keeps it a notch below the top mark.
Proton for Business
Shared calendars with an availability view, built-in appointment booking, encrypted Docs and Sheets with real-time co-editing even for people without an account, Drive storage and Meet video meetings for up to 100 participants all sit in the bundle, with apps for web, desktop and mobile. But we found no public information on CalDAV or CardDAV sync, a company-wide shared address book, tasks, room or resource booking, or Outlook calendar and contacts sync — so for an office that lives in Outlook, the shared calendar would depend on Proton's own apps.
Security, encryption & compliance archiving
Microsoft 365 Business
The compliance side is what I would want behind a Kanzlei: retention labels and policies across Exchange, SharePoint, OneDrive and Teams, legal holds with stated limits, records with proof of disposition for up to seven years, data loss prevention, S/MIME and Purview message encryption, phishing, spam and malware protection, deleted-item recovery, and archives growing to 1.5 TB. But we found no public information on certifications such as ISO 27001 or BSI C5, GoBD-compliant archiving, statements on TLS or encryption at rest, enforced two-factor sign-in or passkeys, or a transparency report on authority requests.
Proton for Business
End-to-end and zero-access encryption, PGP working inside Outlook, Apple Mail and Thunderbird, enforced two-factor, Proton Sentinel, open-source apps independently audited, a bug bounty, ISO 27001 with the auditor's accreditation body named, SOC 2 Type II and a transparency page on authority requests are all documented. We found no public information on GoBD-compliant audit-proof archiving, legal hold, eDiscovery or restore of deleted mail — organization-wide data retention rules exist, but for a German tax practice the audit-archiving question stays open.
Administration, identity & partner management
Microsoft 365 Business
Whoever runs our IT gets the Microsoft 365 admin center, the Exchange admin center and remote PowerShell, provisioning of users, groups and teams by script or through the Graph REST API, full integration with Microsoft Entra ID with group policies and conditional access, ActiveSync device policies, usage reports and a Message Center for announcements. We found no public information on single sign-on explicitly, SCIM provisioning, remote wipe, exportable audit logs or partner accounts managing several customers, and no support response times — only sales phone and chat hours and developer forums.
Proton for Business
Three admin roles with a full permission matrix, SAML single sign-on with Okta and Microsoft Entra ID, a documented SCIM 2.0 provisioning API covering users and groups, exportable activity logs, and admin-enforced 2FA and password policies are all there, backed by priority support, phone support from six users, 24/7 live chat and a 99.95% uptime SLA with service credits. We found no public information on mobile device policies with remote wipe, reseller or multi-customer partner accounts, or stated support response times.
Migration, open standards & exit
Microsoft 365 Business
Getting our old mail across is documented properly: cutover, staged and hybrid Exchange migrations, IMAP migration from Gmail, Exchange and Outlook.com, a PST import service by network upload or drive shipping, self-import of contacts, FastTrack specialists and partner help, plus deletion of all associated data when the subscription is cancelled. Two honest cautions for a firm that cannot lose a single client thread: with IMAP only mail folders move and contacts, calendar items and tasks must be handled another way, and mail arriving at the source after migration is not migrated; we also found no public information on open document formats, an organisation-wide export by the admin, or a stated data-return period.
Proton for Business
The Easy Switch tool imports mail and contacts from a supported provider or any IMAP connection, calendars arrive encrypted, free guided live support for the move is offered, mail exports to EML and MBOX with a command-line export tool, and deletion of data when the contract ends is stated. But the documentation itself says MBOX files cannot be imported directly — a Thunderbird local-folder workaround is needed — and that messages invalid per RFC standards will not import, and we found no public information on calendar export, whole-organisation export by the admin, or coexistence during the move. Workable, but not a documented guarantee that not a single client thread survives the switch.
European sovereignty
Microsoft 365 Business
The EU Data Boundary is documented in real detail — mailboxes on named Microsoft datacentres in Germany, the Netherlands, Austria and other EU and EFTA countries, with sign-up location and billing address deciding whether the tenant is in scope — and the captured pages acknowledge limited transfers outside the boundary. But the chain beyond hosting stays dark: we found no public information on the contracting entity or an EU representative, a data processing agreement, the subprocessors or any certifications, and the vendor itself is Microsoft Corporation of Redmond, Washington.
Proton for Business
Proton AG in Geneva, supervised by the non-profit Proton Foundation, is the contracting party, its data centres are stated to be exclusively in Europe, an EU representative sits in Luxembourg, a data processing agreement is published, and ISO 27001 and SOC 2 Type II are stated. The subprocessor list is unusually open — payments through Stripe, Chargebee and PayPal in the United States, support through Zendesk in the United States and ProtonLabs in Taiwan and North Macedonia, with standard contractual clauses named for some — but the data centres themselves are not named and the contracting entity is Swiss, not EU, so the chain is European rather than EU end to end.
Pricing transparency
Microsoft 365 Business
Prices are public per user with VAT treatment stated — Business Basic at 6,07 € Benutzer/Monat on annual billing with auto-renewal and prices zzgl. MwSt., the Standard and Premium offerings shown at 20,36 € and 27,73 € bundled with Copilot Business — and shared mailboxes and conference rooms need no subscription at all, with mailbox and OneDrive storage stated per plan and a 7-day withdrawal right. We found no public information on monthly versus annual billing differences, minimum users or term, or the price of a Standard or Premium seat without the Copilot bundle, so the exact second-year cost of what we need is not computable from these pages alone.
Proton for Business
Workspace Standard at €12.99 and Premium at €19.99 per user per month with 1 TB and 3 TB per user, the monthly-billing figures of €14.99 and €24.99 for comparison, exact annual billing amounts of €155.88 and €239.88, VAT treatment including reverse charge for business plans, a 30-day money-back guarantee and a 14-day trial are all public. Still open are the price of add-ons such as the Scribe writing assistant on the lower plan and extra aliases, any minimum number of users, and how long the advertised up-to-20%-off discount lasts — the terms say the then-current price applies at renewal, which is exactly the second-year-price question I need answered before signing.
Sovereignty, side by side
Dimension
Microsoft 365 Business
Proton for Business
Legal entity
Not determined
Not determined
Hosting location
Not determined
Not determined
Hosting options
Not determined
Not determined
Open source
Not determined
Not determined
Data processing agreement
Not determined
Not determined
Transfer impact assessment
Not determined
Not determined
Facts, side by side
Only facts both products carry under the same definition — anything else would not be a fair row.
Questions about Microsoft 365 Business and Proton for Business
Which is better, Microsoft 365 Business or Proton for Business?
As of 6 Nov 2026, the panel rates Proton for Business higher: 3.5/5 against 3/5. Weighted by what each judge cares about, 4 of the 6 judges pick Microsoft 365 Business and 2 pick Proton for Business. Which one fits depends on the criteria that matter to you; the table on this page shows both side by side, and each judge’s reading has its own page. Both were scored by the same AI bench under the same rubric, from public evidence only, as the methodology describes.
Is Microsoft 365 Business or Proton for Business European?
Microsoft 365 Business is not European by provenance (Rest of world). Proton for Business is European (UK / wider Europe). Provenance is read from each company’s own legal pages: who builds it and who owns it.