ATP licenses for shared mailboxes?

Brass Contributor

I know shared mailboxes don't require and ATP license but say I have a user (Bob) that has a mailbox with his own ATP license but he's also a member of a shared mailbox "". Will he be protected under his mailbox ATP license for any emails coming into the info@ shared mailbox or will I need to apply an ATP license to the Info shared mailbox to protect all members?

13 Replies



AFAIK you need to apply the ATP license to the shared mailbox.. without that your mailbox is not protected by ATP.




Robin Nishad

@PS_83  ATP is a Feature which does the additional sentinel work for individual mailboxes at the Backend level & not User Level. So if i have access to a Mailbox, doesn't mean the features available because of benefit license (like ATP or EO Plan 2 archiving ) would be applicable to mine as well. ATP is available for per mailbox level usage and hence doesn't protect Owner's or Delegate access mailboxes.


Please refer -


Cheers !

Ankit Shukla



When are licenses required for Shared Mailboxes? Licenses are required for the shared mailbox for the following: Increasing the shared mailbox size limit to 100GB requires Exchange Plan 2 (or Plan 1 + Exchange Online Archiving [EOA]). Enabling E3/EXO P2 capabilities (for example, applying a basic mail retention policy) Exchange Plan 2 (or Plan 1 + EOA). Enabling E5 capabilities (for example, automatic retention or classification, Microsoft Defender for Office 365 (previously O365 ATP)) requires a license that includes the rights to those capabilities (for example, E5 Compliance, E5 Information Protection & Governance, E5 Security).

@PascalDBX It's a bit confusing.


Let's say Bob leaves the company. Prior to leaving, he had a 365 business standard license + Defender license. We convert his mailbox to a shared mailbox and give access to it to another user. Since it's been converted to shared, we don't need to apply the 365 Business Standard license to his user account but do we need to leave the defender license?


I'm asking because if you create a fresh shared mailbox, there are no options to apply a license





My text is the Microsoft official license rules text.

If a mailbox shared or not - use for example Defender ATP - customer need to pay for the license.


Ground rule:

If you get benefit of the service - you need to pay for the licence.


@PascalDBX How do you apply it to a shared mailbox that wasn't converted from a user mailbox? There are no license options.

@PS83 You don't and can't apply it, you just need it purchased.



[SOLVED] Can you please clarify Office 365 advanced threat protection licensing - Spiceworks

I was looking for how to licence ATP on 5 shared mailboxes (info@, invoice@, mailing@, etc) as the 11 users of my customers have all ATP and I want them not to have receiving unprotected mail in the shared mailboxes. Its a huge disadvantage that shared mailboxes need to purchase Exchange online first to make use of ATP. As 2 other vendor service (backup, auto signatures) licenses count only the Office 365 Mailboxes this will result in a huge price explosion for adding 5 protected shared mailboxes. It will cost then € 11,70 / mailbox just to have ATP added to the shared mailbox. Not a good thing and can (will?) hold back to protect these shared mailboxes.

@Rob Ellis @Hello friend can you send me the liason licence 

Hi Paul,

For Microsoft Defender for Office 365 Plan 1 tenants, licenses must be acquired for users or mailboxes falling under one or more of the following scenarios:
- Any user that accesses a mailbox that benefits from Defender for Office 365 protections.
- Shared mailboxes that benefit from Defender for Office 365 protections.
- If Safe Attachments protection for SharePoint, OneDrive for Business, or Teams is turned on, all users that access SharePoint, OneDrive for Business, or Teams.
- Any user that uses Microsoft 365 Apps or Teams when Safe Links protections are enabled.


I have same question (but few years back, not sure it's the latest), it was checked with Microsoft that ATP license was no longer required for shared mailboxes while it was protecteda  by licensed one