Built-in Exchange protection

Immune vs Microsoft 365

Keep Microsoft 365 for employee mail. Add Immune in front of the addresses you publish, where strangers must reach you and content filters are easiest to blend into.

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Capability	Immune	Microsoft 365
Where it shines	Open public and shared addresses	Day-to-day employee mailboxes in the tenant
First-time strangers	Challenge before delivery	Deliver, junk, or quarantine based on Microsoft scores
Works beside M365	Yes (MX or forward into Immune, then to M365 or a helpdesk)	Native to the tenant
Extra seats	Only for inboxes you choose to protect	Tied to Microsoft licensing

Choose Immune when

Public and shared inboxes are the pain

Defender already runs, but contact@ and support@ remain noisy.
You want a stricter gate for published addresses without changing how employees get mail.
Some protected addresses should land in Intercom or Help Scout, not only Outlook.

Microsoft 365 may still fit when

You need something else

You only need Microsoft's default protection for internal and known contacts.
Security policy must stay entirely inside the Microsoft admin center.

vs SpamHero vs MailRoute vs Proofpoint vs Mimecast vs Barracuda vs SpamTitan vs Google Workspace vs Radr vs SaneBox

Protect the inboxes filters leave open

Put a challenge gateway in front of support@, contact@, and the other addresses you publish.

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Immune vs Microsoft 365

Different jobs

Public and shared inboxes are the pain

You need something else

See Immune against other tools

Protect the inboxes filters leave open