Do we need extra licenses Microsoft Defender for Office 365 (Plan 1) for shared mailboxes?

Dimitris P Kepenos 50 Reputation points
2024-12-18T10:42:26.73+00:00

Hello.

I would like to confirm that I understand correctly the licensing regarding standard mailboxes for users and shared ones. Microsoft Defender for Office 365 service description.

We have 55 users and 10 shared mailboxes that some of the users have together.
We have 55 licenses for Microsoft 365 Business Standard and 55 licenses Microsoft Defender for Office 365 (Plan 1). One of each for every user.

My understanding is that if the standard user has the Microsoft Defender for Office 365 (Plan 1) license then the shared mailbox does benefit. The only catch is that every user has to have the Microsoft Defender for Office 365 (Plan 1) license otherwise even if one doesn't have it the share mailbox won't be protected.

Or I'm mistaken and we need +10 licenses of Microsoft Defender for Office 365 (Plan 1) for the shared mailboxes?

Kind regards.

Exchange Online
Exchange Online

A cloud-based service included in Microsoft 365, delivering scalable messaging and collaboration features with simplified management and automatic updates.

Microsoft 365 and Office | Install, redeem, activate | For business | Windows
Exchange | Licensing
Exchange | Licensing

The framework for legally deploying and using Microsoft Exchange Server or Exchange Online, based on server and client access models.

0 comments

Answer accepted by question author

Anonymous
2024-12-19T07:16:17.33+00:00

Hi,@Dimitris P Kepenos

Thanks for posting your question in the Microsoft Q&A forum.

If all users that have access to the shared mailboxes have a Microsoft Defender for Office 365 license, then the shared mailboxes will be automatically protected.

This means if all 55 of your users have a license for Microsoft Defender for Office 365 Plan 1, and these users are the ones accessing the 10 shared mailboxes, then the shared mailboxes should be protected without requiring additional licenses specifically for the mailboxes.

However, if you were to have a user without Defender for Office 365 who needs to access a shared mailbox, that mailbox would not be protected by Defender features until that user is also licensed.

User's image

You can refer to this link for details:https://learn.microsoft.com/en-us/office365/servicedescriptions/office-365-advanced-threat-protection-service-description?source=recommendations#licensing-terms

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Was this answer helpful?

2 people found this answer helpful.

1 additional answer

Sort by: Most helpful
Most helpful Newest Oldest
  1. Oliver Lindsay 0 Reputation points
    2026-01-07T10:58:13.47+00:00

    The answer given is not correct if you want to be license compliant, however defender for 365 features are applied by default tenant wide, regardless of whether all accounts are licensed for it.

    Any mailbox that uses Defender for 365 should have a license. either as part of a bundle like Business Premium, or as a standalone.

    Official MS guidance can be found here: https://learn.microsoft.com/en-us/office365/servicedescriptions/microsoft-365-service-descriptions/microsoft-365-tenantlevel-services-licensing-guidance/microsoft-365-security-compliance-licensing-guidance

    Was this answer helpful?

    1 person found this answer helpful.
    0 comments

Your answer

Answers can be marked as 'Accepted' by the question author and 'Recommended' by moderators, which helps users know the answer solved the author's problem.