Which email security vendor works well with Microsoft 365?

Mimecast and Microsoft Defender are a common combination. Mimecast handles filtering and quarantine while Defender provides the Microsoft 365-side protection. KnowBe4 is also worth considering separately for phishing simulations and user training.

Proofpoint has worked well for us for years, including in an environment of roughly 100 seats. That said, experiences vary quite a bit between the Enterprise and Essentials offerings, so I’d compare the exact product tier and support level. Other organizations in the discussion reported inconsistent results, so a trial is probably worthwhile.

For a 100-user Microsoft 365 setup, I’d first evaluate whether Defender for Office 365 already covers what you need. It comes with some licensing plans and avoids adding another mail-flow hop or another console. The important part is configuring DMARC, tightening allow lists, and making sure user safe-sender rules cannot bypass security policies.

We moved from Mimecast to Avanan, which is now Check Point’s email security product. It has been excellent for phishing and impersonation protection, and the post-delivery remediation is especially useful. We have also seen it deployed successfully in environments ranging from a few hundred users to several thousand.

Barracuda has been solid and reasonably priced for us, with good support and both cloud and gateway options. Abnormal AI, IRONSCALES, Sophos, Mesh, and INKY also came up as alternatives. The best choice depends on whether your main problem is bulk spam, credential phishing, impersonation, or removing malicious messages after delivery.