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 IT Administrator
IT administrator at a machine builder in Baden-Württemberg with three hundred mailboxes, an on-premises Exchange that reaches end of support, and Active Directory as the source of every account. Wants Outlook to keep working without a plug-in nobody maintains, shared mailboxes and room booking, single sign-on and directory sync, mobile devices that can be wiped, an API for provisioning, and a migration that moves calendars and permissions, not only mail.
Microsoft 365 Business
This judge's pick
Proton for Business
Criterion by criterion
Mail, domains & deliverability
Microsoft 365 Business
Exchange Online is documented as a full hosted mailbox platform: quotas of 50 GB and 100 GB per plan (2 GB for Kiosk), default message sizes of 35 MB sending and 36 MB receiving with administrator-configurable limits up to 150 MB, anti-spam and anti-malware with multiple engines across all plans, quarantine an administrator manages, shared mailboxes up to 50 GB without a license, ActiveSync policies, and custom outbound routing with SMTP relay. That covers the working set for my three hundred mailboxes. We found no public information on SPF, DKIM, DMARC or MTA-STS, catch-all or plus addressing, or the delivery reputation of the outbound infrastructure, so it stays below the top level.
Proton for Business
Custom domains with SPF, DKIM automatic key rotation and DMARC are well documented, catch-all and email groups are included, and spam filtering, filters and automatic replies are stated. Outlook, Thunderbird and Apple Mail are reached only through the locally installed Bridge application exposing IMAP and SMTP — client software on every PC rather than a native protocol — and we found no public information on shared mailboxes with delegated send-as, an admin-reviewable quarantine, or stated send and attachment limits.
Calendar, contacts & office apps
Microsoft 365 Business
Conference room management, resource mailboxes, calendar sharing and federated sharing are documented, and the API reaches calendar data in shared as well as primary mailboxes, which covers the delegation model I run today. Word, Excel, PowerPoint and Outlook ship for desktop, web and mobile in the same plans, with Teams, 1 TB OneDrive per user, and global address lists and offline address books for the company directory. We found no public information on browser co-editing, video meetings, cross-organisation free/busy or accessibility conformance, so I cannot place it at the top level.
Proton for Business
Shared calendars with an availability view, appointment scheduling, browser co-editing of documents and spreadsheets with external collaborators, Drive storage with expiring protected links, and Meet video conferencing are all in the bundle with web and mobile apps. We found no public information on room and resource booking, delegated calendar access, CalDAV or CardDAV sync, Outlook calendar and contacts synchronisation, a company-wide address book or tasks.
Security, encryption & compliance archiving
Microsoft 365 Business
S/MIME signing and encryption, message encryption with a 100 MB limit, and single item and deleted mailbox recovery are documented, and the retention side is unusually deep: retention policies across Exchange, SharePoint, OneDrive, Teams and Copilot locations, up to 1,800 policies per tenant, 50 holds per mailbox, record declaration with proof of disposition for up to seven years, and content search with label conditions. We found no public information on two-factor enforcement, encryption at rest, certifications such as ISO 27001 or BSI C5, GoBD-compliant archiving, or a transparency report on authority requests, so the compliance archiving is better evidenced than the security attestations.
Proton for Business
End-to-end and zero-access encryption the provider states it cannot decrypt, PGP in Outlook, Apple Mail and Thunderbird, admin-enforced two-factor, per-team retention rules, ISO 27001 with the accreditation body named, SOC 2 Type II and independently audited open-source apps are documented. We found no public information on GoBD-compliant archiving, legal hold, eDiscovery, or a stated restore period for deleted mail.
Administration, identity & partner management
Microsoft 365 Business
The Microsoft 365 admin center, Exchange admin center and remote PowerShell are documented, Exchange Online integrates fully with Microsoft Entra ID with group-policy management, and API provisioning is strong: Microsoft Graph with SDKs, and PowerShell to provision users, groups and teams, pull usage reports and send security alerts. Mobile devices run under ActiveSync policies with documented device and deletion limits. We found no public information on directory synchronisation with Active Directory, SCIM, exportable audit logs, reseller accounts managing several customers, or support response times, which is what I would still need to run this for a machine builder.
Proton for Business
Three granular admin roles with a documented permission matrix, SAML single sign-on with Microsoft Entra ID and Okta, a documented SCIM 2.0 provisioning API, exportable activity logs, a 99.95 percent SLA with service credits and phone support from six users cover most of what I run. We found no public information on mobile device policies with remote wipe, reseller or multi-tenant partner accounts, or support response times.
Migration, open standards & exit
Microsoft 365 Business
Migration from my on-premises Exchange is documented three ways — cutover for up to 2,000 mailboxes (realistically 150), staged for Exchange 2003/2007 beyond 2,000, and hybrid for gradual moves keeping both on-premises and online mailboxes — plus IMAP from Gmail and Exchange, a PST import service by network upload or drive shipping, cross-tenant migration, Express migration and FastTrack specialists. The IMAP path is explicitly limited to mail folders, with contacts, calendar items and tasks left to the user. We found no public information on permissions or free/busy moving during coexistence or on a data return period after cancellation; deletion of all associated data on cancellation is stated.
Proton for Business
Easy Switch imports mail and contacts from a supported provider or IMAP, calendars are imported too, guided live support is free, and export runs to EML and MBOX down to a command-line tool that restores the same configuration, with deletion of our data at the end of the service committed in the processing agreement. We found no public information on an organisation-wide migration carrying permissions and delegates with free/busy coexistence; MBOX imports need a Thunderbird detour in batches, and no admin-level export of the whole organisation is described.
European sovereignty
Microsoft 365 Business
The EU Data Boundary documentation commits Microsoft to store and process customer data for Microsoft 365 tenants with an EU or EFTA sign-up location, in datacenter countries including Germany, France, the Netherlands and Ireland, with pseudonymised system logs and minimum-retention policies for each log type. The parent is a US company, the same documentation states customer data will continue to be transferred outside the boundary in limited circumstances, and Multi-Geo customers are out of scope. We found no public information on a data processing agreement, an EU contracting entity, or a subprocessor list with locations.
Proton for Business
Proton AG in Geneva under the non-profit Proton Foundation is the contracting entity, data centres are exclusively in Europe, an EU representative sits in Luxembourg, a data processing agreement restricting transfers to Switzerland, the EU and adequacy countries is published, and ISO 27001 is stated. Subprocessors are listed with their locations — support and payment partly in the United States with contractual clauses as safeguard — though the data centres themselves are not named.
Pricing transparency
Microsoft 365 Business
Exact figures are public — Business Basic at 6,07 € per user per month with annual billing, Standard and Premium at 20,36 € and 27,73 € (both shown bundled with Copilot Business), all excluding VAT — with the one-month trial conditions, a 7-day withdrawal right, cancellation through the admin center, mailbox quotas per plan, 1 TB OneDrive per user, and shared mailboxes and conference rooms without a subscription. We found no public information on monthly versus annual billing comparison, the plan prices without Copilot, or add-on prices such as the 100 GB shared mailbox upgrade, extra storage or additional domains, so I cannot fully compute the annual cost for three hundred mailboxes.
Proton for Business
Both workspace tiers are priced per user with monthly and yearly figures side by side (Standard €12.99 against €14.99 monthly, Premium €19.99 against €24.99), storage per user, billing cycles, trial, refund and VAT or reverse-charge treatment stated. The Scribe add-on carries no price on the plans page, a minimum user count is not stated, and enterprise is a custom quote, so the full annual cost still needs one conversation.
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.