FrozenSpam vs Microsoft 365 Defender
Is FrozenSpam complementary to Microsoft 365 Defender? Honest comparison. Updated May 2026.
One-sentence verdict — Microsoft 365 Defender filters mass spam well. FrozenSpam sits in front and adds challenge-response + exposed outbound auto-WL + France hosting, for the SMB segment where Defender Plan 1/2 isn't included in the base subscription.
How it works together
You configure your M365 MX to point first to FrozenSpam, then FrozenSpam relays to Microsoft. You keep your Exchange Online, Outlook clients, Teams — nothing changes. FrozenSpam filters upstream.
Detailed comparison
| Criterion | FrozenSpam (upstream) | Native M365 Defender |
|---|---|---|
| Mass anti-spam | ✓ DNSBL + SPF/DMARC | ✓ Exchange Online Protection included |
| Advanced anti-phishing | CR requires human validation | ≈ Defender Plan 1/2 (paid separately) |
| Exposed outbound auto-WL | ✓ Documented | ≈ Implicit via Outbound Connector |
| Spam in your inbox? | No, blocked upstream | Sorted into Junk folder |
| Additional cost | €4.90-2.90/box/month (anti-spam only) | $2-5/user for Defender Plan 1/2 |
| Hosting | Pure France | Multi-DC EU, possible US transfers |
| Explorable logs | ✓ Live dashboard | ✓ Defender portal |
| GDPR | Simple DPA | Complex Microsoft DPA |
What M365 Defender does better
- Native M365 integration — Attachment detonation chamber, Safe Links URL scanning, integrated phishing training.
- Microsoft cybersecurity suite — Defender integrates antimalware, Conditional Access, Identity Protection.
- Enterprise volume — Handles tens of thousands of M365 boxes.
- If you already have M365 E5, Defender Plan 2 is included — no extra cost.
What FrozenSpam adds in complement
- Targeted spear-phishing blocked — CR requires human reply. Defender Plan 1 doesn't do this (Plan 2 has attack simulation but it's not CR).
- Exposed outbound auto-WL — Contractual zero false-positive guarantee on your initiations.
- Pure France hosting — Without possible US transfer, vs Microsoft where it's complex to guarantee.
- The Junk folder disappears — No more "did I miss a mail in Junk?". Spam doesn't arrive.
- Cheaper for SMBs than Defender Plan 1 + simpler to configure.
- Transparent 5-layer architecture documented.