After listening to customer feedback and suggestions, Exchange Online is making some key changes to the mailbox auditing feature for Office 365 commercial users.

  1. Mailbox audits will be stored for all user mailboxes within the commercial service by default.
  2. The default audit configuration will change and include more audit events.


Why is this change happening?

These enhancements and modifications are a part of Microsoft's commitments to improve the security tooling available to our customers and to ensure that our customers have access to critical audit data to investigate security incidents in their environment when required.


Enabling mailbox auditing by default addresses a specific pain-point with mailbox audit administration today, as Exchange administrators must configure the AuditEnabled setting on each mailbox to be audited after it is provisioned.  In support of Microsoft's commitment to providing our customers with an easy-to-use set of security features, Customers will no longer be required to configure mailbox auditing on a per-mailbox basis, and instead will be able rely on a tenant-wide configuration to enable or disable mailbox audit event collection.  Mailbox events will be stored on the all user mailboxes automatically without required action.


In addition, we plan to expand the default set of audit actions to include more of the currently available Owner and Delegate events. If your mailbox configurations rely on the default settings for AuditOwner, AuditDelegate and AuditAdmin actions, your mailboxes will begin to audit according to the updated defaults. If your Exchange administrator has in the past configured mailboxes with a different set of distinct events, those mailboxes will still follow the configuration that was elected and will not be overridden.   We are frequently adding to the available mailbox audit actions, and as we continue to add audit capabilities, these audit actions will be added to the default as well. A recent example was the introduction of the audit action for the creation of new Inbox Rules and Calendar delegation settings. We believe that auditing these actions can help our customers trace activity on the mailboxes within their service to a more complete degree. 


When will this happen, and what do I need to do?

Over the next several months, we will enable the default-auditing configuration on all tenants with a steady ramp-up with all commercial customers to be covered by the end of the calendar year.  At that time, there is nothing you need to do for the service to begin storing your user's audit events. And if you have already enabled mailbox auditing in Exchange on your user's mailboxes and are doing so for all new mailboxes - great! Mailboxes that are configured to audit today will continue to do so.


If the Exchange mailbox audit feature is new to you, please take some time to familiarize yourself with the options for mailbox auditing and learn how to leverage these events for your security investigation scenarios. Mailboxes generating audit records can be found in the Security & Compliance Center's Audit Log interface, or in the mailbox audit log through the Search-MailboxAuditLog cmdlet. Additionally, explore the options available to you for audit actions including the newly-available ones. If you do not intend on relying on the default configuration, consider adding the new audit actions to your configured set.


How can I opt-out of default mailbox auditing?

As we begin rolling out the default-on configuration to tenants worldwide, a tenant administrator has the capability to pre-emptively override and disable all mailbox audits within their tenancy with the Set-OrganizationConfig cmdlet. You may choose to proactively prevent your tenancy's mailboxes from being audited as part of this feature introduction with this setting. If the tenant-wide AuditDisabled setting is true, all settings for mailbox audit will be overridden to ignore audits. We don't recommend you use this - but is available should your business require it.


What actions are recordable with Mailbox Auditing?

Mailbox auditing for Owner actions includes high-value scenarios to investigating a business email compromise, such as:

  • MailboxLogin events – these events are recorded with client access to user mailboxes including protocol access with POP and IMAP
  • Mail actions to Create, Update (edit) a message in any folder, delete actions to include moving a message to the Deleted Items folder or permanently removing messages, and the Copy or Move of a message.  
  • Actions commonly used in attack scenarios: creation of a mailbox’s Inbox Rule, adding Delegates, or delegating Calendar access to another user.

These Owner events will be added to the service’s default mailbox configuration for auditing. Additional events auditable for the mailbox’s Delegation capabilities include further valuable scenarios that will also be added as default:

  • Mails sent on behalf of an individual, in addition to the SendAs action that is currently default
  • A Delegate’s action to delete messages in a user’s mailbox or move them around folders.


How do I….?

Make Modifications to the Audit Actions

If you choose not to rely on the default settings for audit actions, you may add or drop actions from your configuration with the Set-Mailbox cmdlet for individual mailboxes. Once you elect a set of audit events this way, your mailboxes will no longer automatically follow the default service configuration and will need to be updated via PowerShell when Exchange releases new auditable actions.


Disable Mailbox Auditing for All Mailboxes

When your organization begins auditing all mailboxes by default, you may disable all mailbox auditing with this command:

Set-OrganizationConfig -AuditDisabled $true

To re-enable all mailbox audits, run:

Set-OrganizationConfig -AuditDisabled $false


In the default setting, the -AuditDisabled value will be False.


Disable Mailbox Auditing on Some Mailboxes

When your tenancy begins auditing all mailboxes by default, the per-mailbox AuditEnabled setting will be overridden. However, you may still choose to disable audits for a subset of your users if there is a business need. You can elect this option by configuring audit bypass associations on the identities you intend to ignore with the Set-MailboxAuditBypassAssociation cmdlet.


Find more information:



This is a welcome change. Thank you.

Super Contributor

I probably get it right, that if nothing was done about auditing and currently mailboxes are not audited, they should stay that way and only new mailboxes will be audited after this change?

Hallelujah! I cannot believe it took you guys so long to realize this. And yay for the expanded list of events, also much needed. Now can we also get entries in the O365 audit log for mail flow events?

Occasional Visitor

How does one cause mailboxes with existing audit actions enabled to inherit the new default policy?

New Contributor

I wonder if this new audit feature will bring in Read events by the owner. When a mailbox is compromised there is no way to find out which items are touched by the intruder. 


Occasional Visitor

If we leverage the Set-OrganizationConfig -AuditDisabled $true will that just not enable auditing on new mailboxes or will that disable auditing for all mailboxes that have already been enabled?


most of our mailboxes are enabled for auditing and we are not using the standard set of auditing operations.





Regular Visitor

@Omar Droubi


I understand that when you set True for AuditDisable, all organization will not able to audit, but if some mailbox using manual AuditEnable only then will use audit. Therefore, when the AuditDisable is set to False in organization, all mailbox will able to audit.


Sorry if I'm wrong.



Occasional Visitor

Why wouldn't I turn on all possible auditing for all of my mailboxes?  What are the downsides, I bet there are some but I'm struggling to find something concrete online on that.  Can anyone else offer an opinion?  Thanks.

Occasional Visitor

Ability to audit "MessageBind" is a MUST for the investigation of compromised accounts. I hope, MS will take that in consideration.

New Contributor

What will be the default age limit for the auto-enable audit logs? 90 days I suppose. 

It seems the default is 90 days like with Office 365 Unified Audit Logs. But E5 plans will get 365 days soon. But you can always set up with a PowerShell different period. Interested, if the different period will work...

Occasional Visitor

Hi Brandon,

Would you please be able to tell me when this change is due to happen?  This article is from July and we still haven't had this change.

Many thanks

Occasional Visitor

Why are not all audit logs on?Why let users choose the settings?
I think that it is better to turn all parameter ON by default.(For example, "Copy / admin")
Perhaps the mailbox capacity does not increase and it is around 3 KB per 1 record,
What is the difference between ON and OFF items by default?

Frequent Contributor

Hi people, @Brandon Koeller 


Up until now i have custom actions set on my org mailboxes, and this was set each day on a recurring schedule.


Now with auditing by default enabled i have a bunch of questions;

  • Is it safe to Set-Mailbox -AuditEnabled $false on all mailboxes (because it will instead be enabled at the tenant level?
  • Does the auditing by default interfere with my existing custom actions?
  • Is it safe to Set-Mailbox -AuditOwner $null -AuditDelegate $null -AuditAdmin $null on all mailboxes and let the default actions take over?
  • If i want all the default actions + AuditOwner Copy, do i need to simply Set-Mailbox -AuditOwner @{Add="Copy"} for all mailboxes or do i need to explicitly add all actions that i want audited?
  • For a mailbox with default actions currently set, eg. brand new mailbox, with tenant level auditing enabled, will Set-Mailbox -AuditOwner @{Add="Copy"} append to the list of actions or will it overwrite and treat this as the only action?
    PS:  This could be the same as the question above, depending how you read/interpret it. 




I have got more info through my own testing and below i have updated and answered some of my questions above.


  • Is it safe to Set-Mailbox -AuditEnabled $false on all mailboxes (because it will instead be enabled at the tenant level?
    • NO, if you Set-Mailbox -AuditEnabled $false you will DISABLE auditing.  MS default auditing only works on mailboxes that have auditing enabled.
  • Does the auditing by default interfere with my existing custom actions?
    • NO
  • Is it safe to Set-Mailbox -AuditOwner $null -AuditDelegate $null -AuditAdmin $null on all mailboxes and let the default actions take over?
    • NO, this will overwrite and turn off the default actions set my MS.
  • If i want all the default actions + AuditOwner Copy, do i need to simply Set-Mailbox -AuditOwner @{Add="Copy"} for all mailboxes or do i need to explicitly add all actions that i want audited?
    • Yeah, either "@{Add}" or simply set all the actions you want.
Occasional Visitor

When will this roll out for existing tenants? It's been 6 months since it was announced and our tenant has not received mailbox auditing.