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 Data Protection Officer
Data protection officer for a group of nine medical practices in North Rhine-Westphalia, where a referral letter sent by mail is patient data under professional secrecy. Reads the subprocessor list and the transparency report before the feature page, asks who at the provider can open a mailbox and under which law, and wants encryption the practices can actually use with outside doctors, archiving that satisfies the tax office, and a data processing agreement that names every server.
Microsoft 365 Business
Proton for Business
This judge's pick
Criterion by criterion
Mail, domains & deliverability
Microsoft 365 Business
The service description and limits pages document shared mailboxes reached by delegation, a quarantine with administrator and end-user management, server-side transport and inbox rules, journal rules up to 300, per-plan mailbox storage from 2 GB to 100 GB, and message sizes from a 35 MB default up to 150 MB in Outlook, behind multi-engine anti-spam and anti-malware scanning. For sending referral letters I still found no public information on custom-domain DNS set-up, DKIM or DMARC signing, catch-all, or the delivery reputation of the outbound infrastructure.
Proton for Business
Custom domains come with a documented DNS set-up — SPF, DKIM with a new 2048-bit key every six months, DMARC — plus catch-all, groups, aliases, spam filtering, server-side rules with automated replies, and mail reaches Outlook, Thunderbird and Apple Mail over IMAP and SMTP through the open-source Bridge; storage per user is stated per plan. We found no public information on Exchange ActiveSync or native Outlook connectivity, DMARC reporting, MTA-STS or stated send limits.
Calendar, contacts & office apps
Microsoft 365 Business
The business plans bundle Word, Excel, PowerPoint and Outlook for desktop, web and mobile with Teams calling and 1 TB of OneDrive storage per user, and Exchange brings resource and conference-room mailboxes, calendar sharing and federated sharing, plus an add-in platform across Windows, Mac, Android, iOS and the web. We found no public information on browser co-editing or an interface stated against an accessibility standard.
Proton for Business
Shared calendars with colleague availability, encrypted invitations handled from the mail inbox, external calendar subscription, browser co-editing of documents and spreadsheets, encrypted storage with password-protected expiring links, video meetings for 100 or 250 participants in the bundle, and apps for web, desktop and mobile. We found no public information on room and resource booking, delegated calendar access, or CalDAV/CardDAV and Outlook calendar synchronisation.
Security, encryption & compliance archiving
Microsoft 365 Business
Retention labels and policies across Exchange, SharePoint and Teams, holds up to 50 per mailbox, record declaration with proof of disposition for up to seven years, single-item recovery, S/MIME through the Graph API, Purview message encryption and multi-engine malware scanning are documented — archiving a tax auditor can work with. But the captured pages say nothing about enforced TLS, encryption at rest, enforced two-factor sign-in, a transparency report on authority requests, or any certification with its scope, and nowhere is stated who at Microsoft may open a mailbox and under which law.
Proton for Business
The provider states it can under no circumstances decrypt end-to-end encrypted content, PGP applies automatically in Outlook, Apple Mail and Thunderbird so referral letters to outside doctors stay encrypted, two-factor is enforceable organisation-wide by a security admin, ISO 27001 names its accreditation body and auditor, the apps are open source with independent audits and a bug bounty, and the transparency report confirms only Swiss requests are binding. Team-level retention rules exist, but we found no public information on GoBD-conform audit-proof archiving, legal hold or eDiscovery — for our practices the tax-office archive would have to be supplied elsewhere.
Administration, identity & partner management
Microsoft 365 Business
Administration runs through the Microsoft admin center, the Exchange admin center, remote PowerShell and the Graph REST API with SDKs, integrated with Entra ID for conditional access, identity protection and group policies, alongside ActiveSync device policies with a documented device-deletion limit, usage reports and a message centre. We found no public information on single sign-on protocols such as SAML or OpenID Connect, directory synchronisation, SCIM provisioning, exportable audit logs, or reseller accounts managing several customers.
Proton for Business
Three admin roles are documented down to a permission matrix, single sign-on runs over SAML with Okta and Microsoft Entra ID, SCIM 2.0 provisioning is documented as an API, the activity monitor can be read and exported, users can be marked private against organisation admins, and there is a published 99.95% uptime SLA with service credits plus phone support from six users. We found no public information on mobile device policies with remote wipe or partner and reseller accounts.
Migration, open standards & exit
Microsoft 365 Business
Migration is documented in depth — cutover for up to 2,000 mailboxes, staged and hybrid moves that keep on-premises and online mailboxes alongside each other, IMAP and Gmail migration, cross-tenant moves, PST import by network upload or drive shipping, FastTrack and partner migration — with the IMAP path carrying mail folders only and Exchange Web Services retiring in 2027 in favour of Graph. Deletion of all associated data on cancellation is stated; we found no public information on whole-organisation export in standard formats or a data-return period after cancellation.
Proton for Business
Easy Switch brings mail and contacts across from a supported provider or IMAP with support-team help, calendars import too, and mail leaves again as EML or MBOX via the open-source Bridge, Thunderbird or a command-line export tool for all messages; the data processing agreement provides for deletion when the service ends with a copy request beforehand. MBOX import needs a detour through Thunderbird local folders, and we found no public information on export of the whole organisation by an admin, coexistence during a move, or CalDAV and CardDAV access.
European sovereignty
Microsoft 365 Business
The EU Data Boundary pages commit to storing and processing customer data in named Microsoft datacenters across fifteen EU and EFTA countries for tenants with an EU or EFTA sign-up location, while stating that customer data continues to be transferred outside the boundary in limited circumstances and that Multi-Geo customers are out of scope entirely. Beyond a data protection addendum named in passing, we found no public information on a subprocessor list with locations, an EU contracting entity, or certification scope — so for practices under professional secrecy the chain is only partly evidenced.
Proton for Business
The contracting entity is Proton AG in Geneva under the non-profit Proton Foundation, data centres are exclusively in Europe, disclosure goes only to Swiss authorities, an EU representative sits in Luxembourg, and a published data processing agreement restricts transfers to Switzerland, the EU and adequacy countries while the privacy policy lists subprocessors with their locations; ISO 27001 is stated. Support and payment still run through named processors in the United States and elsewhere — Zendesk, Atlassian, Stripe, Chargebee, PayPal, plus support desks in Macedonia and Taiwan — with transfer guarantees stated for only some, and we found no public information naming the individual data centres.
Pricing transparency
Microsoft 365 Business
Three business tiers are publicly priced — 6,07 €, 20,36 € and 27,73 € per user per month with annual billing and automatic renewal, stated excluding VAT — with a one-month trial requiring a credit card, a seven-day withdrawal right, cancellation through the admin centre, and shared mailboxes and conference rooms requiring no subscription. We found no public information on a monthly-versus-annual billing comparison, prices for archiving, extra storage or single sign-on, or minimum user counts, and the two higher prices are quoted for plans bundled with Copilot.
Proton for Business
Both workspace tiers are public with per-user prices of €12.99 and €19.99 per month on yearly billing, €14.99 and €24.99 monthly, storage per user stated, twelve-month totals of €155.88 and €239.88, a 30-day money-back guarantee, and VAT treatment including reverse charge for business plans. We found no public price for the Scribe add-on or additional storage, no stated minimum users or term, and Enterprise pricing is a custom quote.
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.