AppBreakup
Submit an app

Microsoft Defender for Office 365 alternatives: 4 apps ranked by verified data

Facts checked Nov 8, 2026AppBreakup editorialHow we rankAll email spam filters

Top picks

Common reasons people leave Microsoft Defender for Office 365: only protects Microsoft 365 mailboxes, and investigation and simulation tools need Plan 2. We ranked 4 alternatives by how directly each one replaces Microsoft Defender for Office 365, then by reviews, real visits and how recently each app's facts were checked against its own website. Mimecast currently ranks first.

Quick comparison

#AppPricingVerified priceOpen sourcePlatformsVerified factsScore
1Mimecast logoMimecastPaid—NoWeb4 of 468.8
2Proofpoint logoProofpointPaid—NoWeb4 of 464.8
3Barracuda Email Protection logoBarracuda Email ProtectionPaid—NoWeb4 of 461.8
4SpamTitan logoSpamTitanPaid—NoWeb, Self-hosted4 of 459.4
  1. Mimecast logo

    1. MimecastTop pick

    Best for: Companies wanting a hosted email gateway with continuity and archiving in the same contract

    PaidWeb

    68.8

    score / 100

    Why switch from Microsoft Defender for Office 365

    Independent secure email gateway with archiving and continuity if Microsoft's own filtering isn't enough.

    Pros

    • MX gateway or API deployment, for cloud, on-prem or hybrid mail
    • Mail continuity if your own server goes down
    • Archiving, DMARC and training available on the same platform

    Cons

    • No public pricing; quote through sales or partners
    • Feature set and console can be a lot for small teams
    • Advanced modules cost extra on top of core filtering
    Visit Mimecast Details and reviews
    How this score is calculated
    Editorial fit ×0.3100
    Reviews ×0.363
    Clicks (90 days) ×0.150
    Freshness ×0.15100
    Votes ×0.150

    0 counted reviews, 0 up and 0 down votes. Full formula

    Is Mimecast a good Microsoft Defender for Office 365 alternative?

    Verified facts

    4 of 4 verified
    Deployment
    MX-based or API-based
    Checked Nov 8, 2026mimecast.com(opens source in a new tab)
    Supported mail
    Microsoft 365, Google, on-prem, hybrid
    Checked Nov 8, 2026mimecast.com(opens source in a new tab)
    Email continuity
    Yes
    Checked Nov 8, 2026mimecast.com(opens source in a new tab)
    Customers
    42,000
    Checked Nov 8, 2026mimecast.com(opens source in a new tab)
  2. Proofpoint logo

    2. Proofpoint

    Best for: Large organisations that want gateway or API email protection plus DLP and training from one vendor

    PaidWeb

    64.8

    score / 100

    Why switch from Microsoft Defender for Office 365

    Enterprise email security leader with strong targeted-attack protection and people-centric risk reports.

    Pros

    • Choice of inline gateway or API deployment for Microsoft 365
    • Attachment and URL sandboxing with post-delivery removal
    • Broad suite: DMARC, DLP, awareness training and archiving

    Cons

    • Quote-only pricing with no self-serve plan
    • Built for enterprises; heavy for very small businesses
    • Many features are split across separately sold modules
    Visit Proofpoint Details and reviews
    How this score is calculated
    Editorial fit ×0.387
    Reviews ×0.363
    Clicks (90 days) ×0.150
    Freshness ×0.15100
    Votes ×0.150

    0 counted reviews, 0 up and 0 down votes. Full formula

    Is Proofpoint a good Microsoft Defender for Office 365 alternative?

    Verified facts

    4 of 4 verified
    Deployment
    API or secure email gateway
    Checked Nov 8, 2026proofpoint.com(opens source in a new tab)
    Microsoft 365
    API integration
    Checked Nov 8, 2026proofpoint.com(opens source in a new tab)
    Sandboxing
    Attachments and URLs
    Checked Nov 8, 2026proofpoint.com(opens source in a new tab)
    Supported platforms
    Microsoft 365, Google Workspace
    Checked Nov 8, 2026proofpoint.com(opens source in a new tab)
  3. Barracuda Email Protection logo

    3. Barracuda Email Protection

    Best for: Mid-sized organisations and MSPs wanting email security, archiving and Microsoft 365 backup in one.

    PaidWeb

    61.8

    score / 100

    Why switch from Microsoft Defender for Office 365

    Adds AI threat detection, Microsoft 365 backup and archiving by API, and also covers Google Workspace.

    Pros

    • API connection to Microsoft 365 and Google Workspace with no MX change
    • Bundles archiving and Microsoft 365 backup
    • Rechecks delivered mail and removes threats later
    • MSP-friendly plans and management

    Cons

    • No public per-user prices on the product page
    • Many separate modules make plans harder to compare
    • More than a small team needs for basic spam filtering
    Visit Barracuda Email Protection Details and reviews
    How this score is calculated
    Editorial fit ×0.377
    Reviews ×0.363
    Clicks (90 days) ×0.150
    Freshness ×0.15100
    Votes ×0.150

    0 counted reviews, 0 up and 0 down votes. Full formula

    Is Barracuda Email Protection a good Microsoft Defender for Office 365 alternative?

    Verified facts

    4 of 4 verified
    Deployment
    API connection, no MX change
    Checked Nov 8, 2026barracuda.com(opens source in a new tab)
    Customers
    80,000+ organisations
    Checked Nov 8, 2026barracuda.com(opens source in a new tab)
    Microsoft 365 backup
    Included in bundle
    Checked Nov 8, 2026barracuda.com(opens source in a new tab)
    Platforms protected
    Microsoft 365, Google Workspace
    Checked Nov 8, 2026barracuda.com(opens source in a new tab)
  4. SpamTitan logo

    4. SpamTitan

    Best for: IT teams and MSPs who want managed spam and phishing filtering in front of Microsoft 365 or a mail server

    PaidWeb, Self-hosted

    59.4

    score / 100

    Why switch from Microsoft Defender for Office 365

    Simpler, lower-cost filtering for small businesses and MSPs, with no Microsoft licence tiers to navigate.

    Pros

    • Cloud service, so there's no filtering engine to maintain
    • Sandboxing and dual antivirus for attachments
    • Adds a layer in front of Microsoft 365
    • User quarantine reports and per-domain policies

    Cons

    • No public prices; quotes only
    • Closed source, unlike SpamAssassin or Rspamd
    • Aimed at businesses and MSPs rather than individuals
    Visit SpamTitan Details and reviews
    How this score is calculated
    Editorial fit ×0.369
    Reviews ×0.363
    Clicks (90 days) ×0.150
    Freshness ×0.15100
    Votes ×0.150

    0 counted reviews, 0 up and 0 down votes. Full formula

    Is SpamTitan a good Microsoft Defender for Office 365 alternative?

    Verified facts

    4 of 4 verified
    Owner
    TitanHQ
    Checked Nov 8, 2026spamtitan.com(opens source in a new tab)
    Microsoft 365
    Integrates
    Checked Nov 8, 2026spamtitan.com(opens source in a new tab)
    Sandboxing
    Yes
    Checked Nov 8, 2026spamtitan.com(opens source in a new tab)
    Pricing
    By quote
    Checked Nov 8, 2026spamtitan.com(opens source in a new tab)

The best Microsoft Defender for Office 365 alternative for…

The highest-ranked app in this list for each need.

Mimecast logo

Best Microsoft Defender for Office 365 alternative for most people

Mimecast

Independent secure email gateway with archiving and continuity if Microsoft's own filtering isn't enough.

Proofpoint logo

Best Microsoft Defender for Office 365 alternative for working in the browser

Proofpoint

Enterprise email security leader with strong targeted-attack protection and people-centric risk reports.

Microsoft Defender for Office 365 alternatives: common questions

What is the best alternative to Microsoft Defender for Office 365?

Mimecast ranks first right now. Independent secure email gateway with archiving and continuity if Microsoft's own filtering isn't enough. Proofpoint and Barracuda Email Protection follow it in our ranking.

Microsoft Defender for Office 365 vs Mimecast: what's the difference?

Both Microsoft Defender for Office 365 and Mimecast are paid products. Both run on Web.

Is Microsoft Defender for Office 365 free?

Microsoft Defender for Office 365 is a paid product. Starting price: $2 per user/month (Plan 1, yearly); Plan 2 price: $5 per user/month (yearly); Free trial: 90 days (Plan 2). Checked on Microsoft Defender for Office 365's own site, November 2026.

Is there a free alternative to Microsoft Defender for Office 365?

None of the 4 alternatives we track has a free plan; all are paid, though some offer trials.

Is there an open-source alternative to Microsoft Defender for Office 365?

None of the 4 alternatives in this list is open source.

Why do people switch from Microsoft Defender for Office 365?

The complaints we hear most: only protects Microsoft 365 mailboxes; investigation and simulation tools need Plan 2; annual per-user billing for the add-on.

How is this list ranked?

Every app is scored with the same published formula: how directly it replaces Microsoft Defender for Office 365, reviews (weighted by verification), visits from AppBreakup, how recently its facts were checked against its own website, and reader votes.