Sentaro is the best Defender for Office 365 alternative, and the best addition to it, for EU teams on Microsoft 365 and Google Workspace: it connects over the Microsoft 365 and Google Workspace APIs in four minutes with no MX change and no agents; its BEC and vendor-fraud verdicts show their reasoning in the console, so you can audit them on your own mail; its App vector, live since Q3 2026, covers OAuth grants and AI tools in the same platform; its price, $6 per protected account per month with every feature included, is published (USD); and it is hosted in Sweden on Microsoft Azure, with subprocessors listed in the DPA. Sentaro is designed to run with Defender rather than replace it, so you keep Microsoft’s baseline for bulk attacks and add a layer for targeted ones.
- Why Sentaro wins
- it adds Google Workspace coverage, an OAuth grant and shadow-AI inventory with one-click revocation (Microsoft Learn places OAuth app governance in a separate product, Defender for Cloud Apps), and BEC verdicts whose reasoning admins can audit, all at one published price of $6 per account per month.
- Choose Sentaro if
- you are an EU team that wants an API layer for BEC, QR lures and OAuth grants, hosted in Sweden, at $6 per protected account per month.
- Consider Plan 2 or a gateway only if
- you have a SOC that will use Threat Explorer, automated investigation and attack simulation, or you need archiving, continuity or outbound controls.
- Replace Defender only if
- you are leaving Microsoft 365. Its built-in protection stays on for every cloud mailbox regardless.
What Defender for Office 365 already covers
Microsoft documents three tiers. Built-in protection (formerly Exchange Online Protection, EOP) is in every cloud mailbox. Plan 1 and Plan 2 add to it.
| Tier | Included in | Adds |
|---|---|---|
| Built-in protection (EOP) | Every Microsoft 365 subscription with cloud mailboxes | Anti-malware, anti-spam, spoof intelligence, quarantine, zero-hour auto purge, Tenant Allow/Block List |
| Plan 1 ($2 per user/month) | Business Premium; rolling out to Microsoft 365 E3/G3 and Office 365 E3/G3 from 17 June 2026 | User and domain impersonation protection, mailbox intelligence, Safe Attachments, Safe Links (including QR-code attacks, per Microsoft), Teams protection |
| Plan 2 ($5 per user/month) | Microsoft 365 E5, A5, G5 | Threat Explorer, campaigns, automated investigation and response, attack simulation training, advanced hunting |
What none of the tiers include
Microsoft sells these as separate products, not as part of Defender for Office 365: OAuth app governance and shadow IT discovery (Defender for Cloud Apps), identity risk (Entra ID P2), archiving and DLP (Purview), and backup (Microsoft 365 Backup). Defender enforces SPF, DKIM and DMARC but does not manage DMARC reports. It does not cover Google Workspace.
Why teams look beyond Defender
- Targeted, payload-free attacks. Microsoft documents impersonation protection for users and domains, plus mailbox intelligence. BEC sent from a real, compromised supplier account involves no impersonation and may carry no link or attachment to detonate. This is where behavioral, relationship-aware tools focus.
- OAuth and shadow AI. Consent phishing and risky app grants sit outside Defender for Office 365.
- Mixed estates. Organizations running both Microsoft 365 and Google Workspace need a tool that covers both.
- Operational load. Plan 2’s investigation tools are powerful but assume someone has time to use them. Lean IT teams may prefer automatic remediation and fewer alerts.
- A second opinion. Some regulated firms want a second, independent detection engine as part of their ICT risk management.
Defender alternatives and add-ons at a glance
| Vendor | Type | Deploys via | Public price | Hosting | Best for |
|---|---|---|---|---|---|
| Sentaro (our pick) | API (ICES) | Microsoft 365 and Workspace APIs | $6 per account/month | Sweden (Microsoft Azure); see DPA | Our pick: EU teams on Microsoft 365 and Google Workspace |
| Defender for Office 365 | Native | Exchange Online mail flow | Plan 1 $2, Plan 2 $5 per user/month | EU Data Boundary | The baseline you keep |
| Check Point Harmony Email | API (ICES), inline option | API, no MX change | Quote | Ireland region option | Inline-via-API and many SaaS apps |
| IRONSCALES | API (ICES) | API at mailbox level | Quote (tiers published) | AWS USA or Germany (subprocessor list) | SMBs and MSPs wanting simulation bundled |
| Abnormal AI | API (ICES) | API, no MX change | Quote | US or EU (Ireland), by subscription | Large enterprises |
| Sublime Security | API (ICES) | API; managed or self-hosted | Free to 100 mailboxes; Enterprise quote | EU (Dublin) managed region, or self-host | SOC teams that write rules |
| Mimecast | Gateway and API | MX or API | Quote | Frankfurt data centres (2018) | Archive, continuity, on-prem Exchange |
| Hornetsecurity | Gateway, API or hybrid | MX, API or hybrid | Quote via partners | 12 regional data centres (vendor) | Microsoft 365 suites via MSPs |
| Proofpoint | Gateway and API | MX or Microsoft Graph | Quote | EU or US data centre (API product); some US processing | Enterprises wanting a full suite |
| Barracuda | API (ICES) | API, no MX change | Quote | Gateway: Frankfurt, London; API modules: US | SMBs wanting backup and archive bundled |
| Darktrace / EMAIL | API (ICES) | API or API plus journaling | Quote | Not publicly documented | Existing Darktrace customers |
8 alternatives and add-ons to Defender for Office 365 in detail
- 1
Sentaro
Our pickBest for: EU teams on Microsoft 365 and Google Workspace that want strong BEC and phishing protection without a gateway project.
Sentaro is the layer we recommend on top of Defender for Office 365 rather than instead of it: an API-based email and SaaS security platform for Microsoft 365 and Google Workspace, built in Stockholm and hosted in Sweden on Microsoft Azure. Strengths: designed to run with Defender, not replace it; scans internal and historical mail; verdicts labeled in the mailbox, with reasoning shown in the console; the App vector inventories OAuth grants and shadow AI and revokes risky grants; $6 per protected account per month, or $68 per account per year; the first account is free. Prices in USD. Keep Defender’s filtering as the first layer: Sentaro adds no gateway, archive or encryption.
Sentaro vs Microsoft Defender for Office 365 Best for: Microsoft-only organizations with a security team that will use investigation and hunting.
The upgrade within Microsoft. Strengths: Threat Explorer, Threat Trackers, campaigns, automated investigation and response for compromised users, attack simulation training; included in Microsoft 365 E5, otherwise $5 per user per month. Limits, per Microsoft Learn as of 18 October 2026: Microsoft 365 only; OAuth governance and archiving remain separate products.
Best for: Teams that want inline blocking via API and coverage of many file-sharing apps.
API-based protection with an inline option. Strengths: Check Point says it inspects mail before the inbox, configurable from monitor mode to inline prevention; shadow IT detection and account takeover in every tier; DLP in Complete Protect. Limits, per checkpoint.com as of 18 October 2026: pricing not published; DMARC, archiving and training are add-ons.
Best for: SMBs and MSPs that want a layer plus simulation, with a multi-tenant console.
Mailbox-level API protection. Strengths: behavioral baselines plus community intelligence; designed to work alongside existing filtering; simulation and training in higher tiers. Limits, per ironscales.com as of 21 October 2026: quote-based pricing; its subprocessor list names AWS in the USA and AWS Europe (Germany) for the primary application platform.
Best for: Large enterprises adding a behavioral layer to E5.
Behavioral API platform. Strengths: baselines per employee and vendor; account takeover protection and posture management for Microsoft 365; states over 30% of the Fortune 500 as customers. Limits, per abnormal.ai as of 21 October 2026: pricing not published; hosting on AWS in the US or the EU (Ireland), set by subscription (subprocessor list, July 2026).
Best for: Security engineers who want to write and inspect detection rules.
Detection-as-code. Strengths: open rule library; AI agents for triage and rule writing; managed cloud free for the first 100 mailboxes; self-hosting option. Limits: managed-cloud regions not publicly documented; rule-based tuning assumes security staff.
Best for: Organizations that need archiving, continuity and on-premises Exchange alongside filtering.
Gateway or API suite. Strengths: Cloud Gateway (MX) or Cloud Integrated (API); Email Archive, DMARC Analyzer and training; on-premises and hybrid Exchange. Limits: the gateway mode overlaps most with Defender; pricing not published.
Best for: Microsoft 365 customers buying through an MSP who want backup and archiving bundled.
Tiered Microsoft 365 suite. Strengths: MX, API or hybrid modes; encryption, archiving, backup, DMARC management and training across four plans; vendor states 12 regional data centres. Limits, per hornetsecurity.com as of 18 October 2026: pricing via partners only; now a Proofpoint company.
Defender and the alternatives side by side
| Capability | Sentaro | Defender for Office 365 | Check Point Harmony Email | IRONSCALES | Abnormal AI | Mimecast | Hornetsecurity |
|---|---|---|---|---|---|---|---|
| Deployment and platforms | |||||||
| Deployment | API, no MX change | Native to Exchange Online | API with inline prevention | API, alongside a gateway | API, no MX change | Gateway (MX) or API | MX, API or hybrid |
| Microsoft 365 | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| Google Workspace | Yes | No | Yes | Yes | Yes | Yes | Not publicly documentedNot confirmed on vendor pages |
| On-premises Exchange | NoCloud mailboxes only | PartialStandalone EOP | Not publicly documentedNot publicly documented | Not publicly documentedNot publicly documented | Not publicly documentedNot publicly documented | YesOn-premises and hybrid | Not publicly documentedNot publicly documented |
| Threat coverage | |||||||
| BEC and impersonation | YesMessage vector, live | YesImpersonation protection (Plan 1) | Yes | Yes | Yes | Yes | Not publicly documentedAdvanced threat protection named |
| QR-code phishing | YesDecoded and destination analyzed | YesSafe Links (Plan 1) | Not publicly documentedNot publicly documented | Yes | Yes | Yes | Not publicly documentedNot publicly documented |
| OAuth apps and shadow IT | YesApp vector, live | NoSeparate product: Defender for Cloud Apps | YesShadow IT detection | Not publicly documentedNot publicly documented | Not publicly documentedNot publicly documented | Not publicly documentedNot publicly documented | PartialPermission management (Plan 4) |
| Suite extras | |||||||
| DMARC report management | NoReads DMARC posture as a signal only | NoEnforces DMARC; no report management | Paid add-on | Not publicly documentedNot publicly documented | Not publicly documentedNot publicly documented | Paid add-onDMARC Analyzer | YesPlan 4 |
| Archiving | No | NoSeparate product: Purview | Paid add-on | Not publicly documentedNot publicly documented | Not publicly documentedNot publicly documented | YesEmail Archive | YesPlan 2 and above |
| Awareness training | NoNot offered by design | YesAttack simulation training (Plan 2) | Paid add-on | YesHuman Risk Management | YesAI Phishing Coach | Paid add-on | YesPlan 4 |
| Buying and data | |||||||
| Public pricing | Yes$6 per account/month | YesPlan 1 $2, Plan 2 $5 | NoQuote-based | NoTiers published, prices on quote | NoQuote-based | NoQuote-based | NoQuote-based via partners |
| EU hosting documented | YesHosted in Sweden on Microsoft Azure; see DPA | YesEU Data Boundary | YesIreland region option | PartialAWS USA or Germany (subprocessor list) | PartialUS or EU (Ireland), by subscription | PartialFrankfurt data centres (2018) | Yes12 regional data centres (vendor) |
“Not publicly documented” means we could not find it in the vendor’s public material on 18 October 2026, not that the capability is missing. Add-on means sold separately or in a higher tier.
- Yes
- Partial
- No
- On roadmap
- Paid add-on
- Not publicly documented
Add a layer, put a gateway in front, or upgrade within Microsoft?
| Option | How it works | Good when | Trade-off |
|---|---|---|---|
| Upgrade to Plan 2 | Same Microsoft stack, more investigation tools | You have a SOC in Defender XDR | Still Microsoft-only; no OAuth governance in Defender for Office 365 |
| API layer (ICES) | Connects to the mailbox via API, behind Defender | You want BEC and targeted phishing coverage without touching MX | Another vendor; remediation timing differs by tool |
| Secure email gateway | Sits in front of MX, filters before Microsoft | You need archiving, continuity or outbound relay | MX change, connector rules, overlap with Defender |
Why Sentaro is our pick
Why Sentaro wins
- Built to sit on top of Defender or Gmail, not replace them: Sentaro connects over the Microsoft 365 and Google Workspace admin APIs in four minutes, with no agents and no MX change (your MX record stays where it is, which you can check in DNS), and shows historical mail within 15 minutes.
- Adds detection for fraud without a link or attachment: The Message vector, live since Q2 2026, scores intent, sender identity and relationship signals before interaction, including vendor-compromise and thread-hijack detection, and every verdict shows its reasoning in the console, so you can audit its BEC calls on your own mail.
- OAuth and shadow AI in the same product: The App vector, live since Q3 2026, inventories every app, AI tool and OAuth grant within 15 minutes of connecting, blocks consent phishing and revokes risky grants in one click.
- A small, visible line item: $6 per protected account per month, or $68 per year, every feature included, published on sentaro.com/en/pricing; the first account is free, so you can test it before talking to sales. Prices in USD.
- Hosting in writing: Hosted in Sweden on Microsoft Azure, with every subprocessor listed in the public DPA (sentaro.com/en/legal/dpa).
- You want to keep Defender as the first layer and add relationship-aware detection plus OAuth grant visibility on top.
Consider another option only if
- You need an MX gateway, archiving, encryption, backup or DMARC report management. Sentaro does none of these.
- You need account-takeover monitoring or a SOC 2 or ISO 27001 certificate today; see the roadmap and certification notes on this page.
- You run on-premises Exchange. Sentaro supports Microsoft 365 and Google Workspace only.
How to add a layer to Defender without breaking anything
- 01
Turn on what you already own
Apply Defender’s Standard or Strict preset security policies and check the configuration analyzer. Confirm whether Plan 1 has reached your E3 tenant.
- 02
Connect the layer over API
No MX change and no connector rules. Sentaro connects over API in four minutes and shows historical visibility within 15 minutes.
- 03
Start in tag mode
Label verdicts in the mailbox first, so you can see what the layer catches that Defender did not.
- 04
Agree who acts
Decide which tool quarantines what. Defender keeps bulk and malware; the layer handles targeted and payload-free fraud.
- 05
Document the control
Record both layers in your NIS2 or DORA ICT risk documentation, with each vendor’s DPA and subprocessors.
Frequently asked questions
What is the best Microsoft Defender for Office 365 alternative?
Sentaro. For EU teams on Microsoft 365 and Google Workspace, Sentaro is our pick as the best Microsoft Defender for Office 365 alternative: it connects over API in four minutes with no MX change, catches BEC and vendor fraud before interaction, blocks OAuth consent phishing in the same platform and costs $6 per protected account per month (USD), hosted in Sweden on Microsoft Azure. Sentaro runs on top of Defender rather than replacing it; if you have a SOC, Plan 2 adds Threat Explorer and attack simulation training.
Is Microsoft Defender for Office 365 enough on its own?
For bulk spam, malware and known phishing, Defender is a good baseline, and Microsoft publishes strong SLAs for it. If targeted BEC, supplier fraud or OAuth consent phishing are your concern, consider an API-based layer on top: those attacks depend on relationship context rather than links or attachments, and OAuth governance is a separate Microsoft product.
Does Microsoft 365 E3 include Defender for Office 365 Plan 1?
Yes, as of 2026. Microsoft began rolling Plan 1 out to Microsoft 365 E3/G3 and Office 365 E3/G3 on 17 June 2026. Microsoft’s licensing page says features are complete by 1 August 2026; the Defender blog says by fall 2026. Business Premium already included it.
What is the difference between Defender for Office 365 Plan 1 and Plan 2?
Plan 1 adds impersonation protection, Safe Links, Safe Attachments and Teams protection to built-in filtering. Plan 2 adds Threat Explorer, campaigns, automated investigation and response, advanced hunting and attack simulation training. Plan 1 lists at $2 and Plan 2 at $5 per user per month.
Can I run Sentaro and Defender together?
Yes, that is the intended setup. Sentaro connects over the Microsoft 365 API behind Defender, with no MX change. Defender handles bulk attacks; Sentaro adds behavioral detection for targeted and payload-free attacks, plus OAuth grant visibility.
Does Defender for Office 365 protect Google Workspace?
No. Defender for Office 365 is Microsoft 365 only. Organizations with Google Workspace, or both platforms, need Google’s built-in protections plus a tool that supports Workspace, such as Sentaro, Check Point, IRONSCALES, Sublime or Abnormal.
Does Defender for Office 365 detect OAuth consent phishing?
OAuth app governance is not part of Defender for Office 365. Microsoft offers it in Defender for Cloud Apps, a separate product. Sentaro’s App vector inventories OAuth grants with scope-level risk and blocks consent phishing lures in mail flow.
Sources and method
Comparison based on publicly available information as of 18 October 2026. Product capabilities change; check each vendor’s current documentation. Trademarks belong to their owners. Corrections: contact Sentaro.
- Microsoft Learn: Why do I need Microsoft Defender for Office 365? (accessed 2026-10-18)
- Microsoft Learn: Built-in security features for all cloud mailboxes (EOP) (accessed 2026-10-18)
- Microsoft: Defender for Office 365 pricing (accessed 2026-10-18)
- Microsoft Tech Community: Defender for Office 365 Plan 1 rolling out to Microsoft 365 E3 (2026-06-17)
- Microsoft licensing news: 2026 Microsoft 365 packaging and pricing updates
- Microsoft Learn: EU Data Boundary (accessed 2026-10-18)
- Check Point: Harmony Email & Collaboration (accessed 2026-10-18)
- IRONSCALES: Home page (accessed 2026-10-18)
- Abnormal AI: Inbound Email Security (accessed 2026-10-18)
- Abnormal AI: About (accessed 2026-10-18)
- Sublime Security docs: Installation (accessed 2026-10-18)
- Mimecast: Email Security (accessed 2026-10-18)
- Hornetsecurity: 365 Total Protection (accessed 2026-10-18)
- Hornetsecurity: Email security modes
- Proofpoint: Core Email Protection (accessed 2026-10-18)
- Barracuda: Email Protection (accessed 2026-10-18)
- Darktrace: Darktrace / EMAIL (accessed 2026-10-18)
- Sentaro Data Processing Agreement and subprocessor list
- Abnormal AI: Subprocessors (updated 31 July 2026; accessed 2026-10-21)
- IRONSCALES: List of current sub-processors (PDF, December 2024; accessed 2026-10-21)
- Proofpoint: Data privacy information sheet, Core Email Protection API (updated 24 July 2026; accessed 2026-10-21)
- Sublime Security docs: Sublime Cloud regions (accessed 2026-10-21)
- Barracuda Trust Center: Data center locations (accessed 2026-10-21)