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 Public Sector IT Lead
Head of IT at a district administration in Bavaria with eleven hundred staff, told by the council to leave Microsoft within three years. Has read what Schleswig-Holstein did and what it cost. Needs mail, calendars and documents that a whole administration can work in, open formats and open source where possible, BSI C5 or ISO 27001 on paper, a provider whose owners answer to European law only, and an exit plan before the contract is signed.
Microsoft 365 Business
Proton for Business
This judge's pick
Criterion by criterion
Mail, domains & deliverability
Microsoft 365 Business
Exchange Online is documented as a full hosted mail platform: mailbox sizes per plan from 2 GB to 100 GB, multi-engine anti-malware and phishing protection on all plans, quarantine an administrator can review, server-side rules and out-of-office replies, ActiveSync device policies, S/MIME signing and encryption, and stated limits for messages, attachments and sending down to transport rules and journal rules. What the captured pages do not show is the domain side — custom-domain DNS set-up, SPF, DKIM, DMARC, MTA-STS — or any statement on the delivery reputation of the outbound infrastructure, which for an authority sending official notices matters as much as the limits.
Proton for Business
Mailboxes on custom domains with a documented DNS walk-through for SPF, DKIM (automatic 2048-bit key rotation every six months via CNAME records) and DMARC, plus catch-all, groups, aliases, unlimited filters and automatic forwarding on both plans; Outlook, Thunderbird and Apple Mail connect through the open-source Proton Mail Bridge over IMAP and SMTP, and storage per user is stated per tier. We found no public information on Exchange ActiveSync or native Outlook (MAPI), DMARC reporting, MTA-STS or DANE, an admin-reviewable quarantine, delegated send-as, plus addressing, or send and attachment limits — a protocol gap that would bite an administration whose staff live in Outlook.
Calendar, contacts & office apps
Microsoft 365 Business
The breadth is documented: conference room management and calendar sharing with federated publishing, global address lists and address book policies, Word, Excel, PowerPoint and Outlook for desktop, web and mobile, 1 TB of OneDrive storage per user, Teams and more than ten further apps, with add-ins across Windows, Mac, Android, iOS and the web. Browser co-editing, free/busy across organisations, delegated calendar access and any statement against an accessibility standard are not documented on the captured pages, so I cannot place it at the top level despite the breadth.
Proton for Business
The bundle is genuinely broad: shared calendars with a colleague-availability view, 25 calendars per user, invitations handled from the inbox, subscription to external calendars, encrypted Docs and Sheets with real-time co-editing even for outsiders without an account, Drive with password-protected expiring links, Meet with recording at 100 or 250 participants, offline file sync, and apps for web, desktop and mobile. We found no public information on CalDAV or CardDAV sync to phones and desktop clients, Outlook calendar sync, room and resource booking with approval, delegated calendar access, tasks, or a company-wide directory and address book — the calendar interoperability a district office runs on. Loss-free editing of Microsoft file formats is also not described, which matters for a Microsoft exit.
Security, encryption & compliance archiving
Microsoft 365 Business
Retention and archiving are documented to audit-grade depth — retain, delete and combined modes, event-based retention, legal holds with stated per-mailbox limits, proof of disposition for up to seven years, record declaration, archive mailboxes growing to 1.5 TB, deleted-item recovery — alongside S/MIME and multi-engine anti-malware. No certification appears on the captured pages — I found no public information there on ISO 27001, BSI C5 or SOC 2 — and encryption in transit and at rest, enforced two-factor sign-in and a transparency report on authority requests are equally undocumented; a council that demands C5 on paper cannot get it from these pages.
Proton for Business
End-to-end encryption with zero access to mail, calendar, files and documents, PGP working inside Outlook, Apple Mail and Thunderbird, enforced two-factor, Proton Sentinel account protection, open-source apps under independent audit, ISO 27001 (auditor type and ANAB accreditation named) and SOC 2 Type II published, and a transparency page stating only binding requests from Swiss authorities are honoured. Organization-wide retention rules with per-team configuration exist and are permission-gated. We found no public information on GoBD-compliant archiving, legal hold, eDiscovery, restore of deleted mail, or BSI C5 — the audit-proof archive a German administration is legally required to run is not documented, which for me is a blocker to check before any signature.
Administration, identity & partner management
Microsoft 365 Business
Administration runs through the Microsoft admin centre, the Exchange admin centre and remote PowerShell, with the Graph API and SDKs for provisioning, usage reports and security alerts, Entra ID integration with group policies, conditional access, identity protection and advanced device management, plus ActiveSync device policies. I found no public information on the captured pages about single sign-on protocols, directory synchronisation, SCIM provisioning, exportable audit logs, reseller accounts managing several customers, or support response times — for eleven hundred accounts across remote sites, that is the part I would have to see before signing.
Proton for Business
SAML single sign-on with Okta and Microsoft Entra ID, a documented SCIM 2.0 provisioning API with operations, error codes and Bearer-token setup, three admin roles with a published permission matrix reaching down to SAML, SCIM, gateways, retention and billing, an activity monitor with export, phone support from six users, and a 99.95% uptime SLA with 10% and 30% service credits published. We found no public information on mobile device policies with remote wipe, partner or reseller accounts managing several customers, usage reports, or audit log streaming to a SIEM. For eleven hundred endpoints, absence of documented device management is the gap I would press hardest on.
Migration, open standards & exit
Microsoft 365 Business
The way in is documented thoroughly — cutover, staged, hybrid and express migrations from Exchange, IMAP migration from Gmail and other systems (though IMAP carries only mail folders, not contacts, calendars or tasks), a PST import service by network upload or drive shipping, FastTrack specialists and partners — and an on-premises Exchange Server edition exists for those keeping mail in their own racks. The way out is thinner: the Graph API offers mailbox import and export and cancellation deletes the data with a seven-day withdrawal right, but an organisation-wide export in open formats, open document formats, open-source code and a contractual data return period are not documented — and Schleswig-Holstein taught us the exit is the expensive half.
Proton for Business
The way in is documented — Easy Switch for mail and contacts from a supported provider or IMAP, calendar import, recommended batches of 100 to 500 messages, and free guided live migration support — and so is the way out: EML and MBOX export via the open-source Bridge and Thunderbird, a command-line export tool for all mail as EML with JSON metadata on Windows, macOS and Linux, deletion of company personal data on cessation of service in the data processing agreement, and all apps open source with public repositories. We found no public information on CalDAV or CardDAV access, export of the whole organisation by an admin, coexistence with free/busy during a move, native open document formats, a self-hosted edition, or a stated data-return period after cancellation. MBOX files also cannot be imported directly and must detour through Thunderbird local folders — workable, but a project for a thousand mailboxes needs to plan for it.
European sovereignty
Microsoft 365 Business
The EU Data Boundary is documented with named datacentre countries including Germany, and Microsoft 365 tenants with an EU or EFTA sign-up location fall in scope — that is real. But the same pages state that data continues to be transferred outside the boundary in limited circumstances, that Multi-Geo customers are excluded from it entirely, and I found no public information on the captured pages about an EU contracting entity, a subprocessor list, a data processing agreement or any certification — an American parent offering an EU region is part of the chain, not the sovereignty my council asked for.
Proton for Business
Proton AG in Plan-les-Ouates under the non-profit Proton Foundation, Swiss governing law with Geneva courts, data centres exclusively in Europe, an EU representative (Proton Europe sàrl in Luxembourg), a published data processing agreement restricting transfers to Switzerland, the EU and adequacy countries with standard contractual clauses as fallback, ISO 27001 stated, and a named subprocessor list with locations and safeguards. The entity is Swiss rather than EU, the hosting infrastructure itself is not named, and support and payment run through processors in the United States (Zendesk, Atlassian, Stripe, Chargebee, PayPal) and North Macedonia and Taiwan. That no foreign authority request is binding without Swiss backing answers my ownership question better than most EU entities — but the chain is transparent rather than purely European, so it sits between the levels.
Pricing transparency
Microsoft 365 Business
Three business tiers carry public per-user monthly prices on annual billing — 6,07 €, 20,36 € and 27,73 € excluding VAT — with trial and cancellation terms stated, the per-user licensing model explicit, and the useful detail that shared mailboxes and conference rooms require no subscription. Monthly versus annual comparison, add-on prices for archiving or extra storage, minimum user counts, migration and support fees and the rate for the usage-based AI functions are not published, so I cannot compute our real annual cost from these pages alone.
Proton for Business
Both workspace tiers are public with per-user price, storage, domain count and annual total — Workspace Standard at €12.99 per user per month billed €155.88 every 12 months with 1 TB, Premium at €19.99 billed €239.88 with 3 TB — monthly and yearly prices compared (€14.99 and €24.99 monthly), VAT treatment for business reverse charge and VAT-ID validation explained, a 30-day money-back guarantee and a 14-day trial stated. The Proton Scribe add-on price, minimum users and contract term are not stated, and Enterprise is a custom quote. I can compute an annual seat cost from public pages alone, but not the full cost with add-ons and terms.
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.