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Exchange Online No valid Azure app found

  • April 9, 2026
  • 3 replies
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Paul G
Explorer
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Hi everyone,

For about a week now, we have 2 failed mailboxes in the Exchange Online backups that have the failure reason "No valid Azure app found. Please run Check Readiness". In the same backups we have 346 mailboxes that show no issues.

Only these 2 mailboxes have issues and I cannot find what is causing this. The mailboxes still exist and are no different from other shared mailboxes.

The logs show no different errors for the mailboxes so I am a bit at a loss. I also see the same issue for multiple Exchange applications.
Does anyone have an idea how to resolve this?

Kind regards,
Paul

Best answer by Syed_S

Hi ​@Paul G 

Good day!

We observed these issue sometime before originating from Microsoft that are impacting certain Exchange mailboxes. Affected users may see the following error in the mailbox status: “No valid Azure app found. Please run check readiness.”

Our team worked with Microsoft and addressed the issue. 

As per latest update from MS, they have fixed this issue.MS ticket(2512220030004127‎)

As per our development team investigation, some tenants are getting more throttled and “No valid app” is for throttling response from Microsoft 

We confirmed that throttling-related failures are transient in nature and that affected mailboxes are retried in subsequent backup jobs.

Our development team is working on improving the error handling for the mailbox backups

Below mailbox may not have MS archive mailbox enabled.

Also this behaviour could be related to recent changes in Exchange Web Services (EWS) by Microsoft.


The DEV team updated like The EWS flags that allow for the use of the API on either the organization and/or user level may have been set during this change to "false" resulting in the denials.

Please verify the status of your EWS access on both the organization level and user level by connecting to the tenant with powershell:

Instructions to connect to PowerShell: https://learn.microsoft.com/en-us/powershell/exchange/connect-to-exchange-online-powershell?view=exchange-ps

Organization Level: 
PS> Get-OrganizationConfig |fl *ews*

User Level:
PS> Get-CASMailbox -ResultSize Unlimited |Where-Object { $_.EwsEnabled -eq $false } | Select-Object DisplayName, PrimarySmtpAddress, EwsEnabled


For resolution, both levels are required to be set to true. The following commands are how to set each respective level:
 
User Level:
PS> Get-CASMailbox -ResultSize Unlimited | Where-Object { $_.EwsEnabled -eq $false } | Set-CASMailbox -EwsEnabled $true
 
Org Level:
PS> Set-OrganizationConfig -EwsEnabled $true
 
Once both are set, please run new backups and monitor accordingly. Please note that it may take time for these rules to propagate through Microsoft's side.

-- Please accessing the Affected Mailbox throughEWS editor
Please download EWS editor, the EWS Editor tool needs to be downlaoded on the access node and will require appid, secret key value for this 
https://github.com/dseph/EwsEditor/releases/download/1.24.0/EwsEditor.1.24.-.bin.zip


 

3 replies

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  • Vaulter
  • Answer
  • April 11, 2026

Hi ​@Paul G 

Good day!

We observed these issue sometime before originating from Microsoft that are impacting certain Exchange mailboxes. Affected users may see the following error in the mailbox status: “No valid Azure app found. Please run check readiness.”

Our team worked with Microsoft and addressed the issue. 

As per latest update from MS, they have fixed this issue.MS ticket(2512220030004127‎)

As per our development team investigation, some tenants are getting more throttled and “No valid app” is for throttling response from Microsoft 

We confirmed that throttling-related failures are transient in nature and that affected mailboxes are retried in subsequent backup jobs.

Our development team is working on improving the error handling for the mailbox backups

Below mailbox may not have MS archive mailbox enabled.

Also this behaviour could be related to recent changes in Exchange Web Services (EWS) by Microsoft.


The DEV team updated like The EWS flags that allow for the use of the API on either the organization and/or user level may have been set during this change to "false" resulting in the denials.

Please verify the status of your EWS access on both the organization level and user level by connecting to the tenant with powershell:

Instructions to connect to PowerShell: https://learn.microsoft.com/en-us/powershell/exchange/connect-to-exchange-online-powershell?view=exchange-ps

Organization Level: 
PS> Get-OrganizationConfig |fl *ews*

User Level:
PS> Get-CASMailbox -ResultSize Unlimited |Where-Object { $_.EwsEnabled -eq $false } | Select-Object DisplayName, PrimarySmtpAddress, EwsEnabled


For resolution, both levels are required to be set to true. The following commands are how to set each respective level:
 
User Level:
PS> Get-CASMailbox -ResultSize Unlimited | Where-Object { $_.EwsEnabled -eq $false } | Set-CASMailbox -EwsEnabled $true
 
Org Level:
PS> Set-OrganizationConfig -EwsEnabled $true
 
Once both are set, please run new backups and monitor accordingly. Please note that it may take time for these rules to propagate through Microsoft's side.

-- Please accessing the Affected Mailbox throughEWS editor
Please download EWS editor, the EWS Editor tool needs to be downlaoded on the access node and will require appid, secret key value for this 
https://github.com/dseph/EwsEditor/releases/download/1.24.0/EwsEditor.1.24.-.bin.zip


 


Paul G
Explorer
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  • Author
  • Explorer
  • April 14, 2026

Hi ​@Syed_S,

I have asked my colleague for EWS and archive mailbox details around the failing mailboxes.

The error does not seem to be caused by load as it will also fail when running a separate backup outside all other backups for office 365.

I will let you know once I have more information.


Paul G
Explorer
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  • Author
  • Explorer
  • April 16, 2026

Hi ​@Syed_S,

My colleague checked and discovered that the 2 failing mailboxes did indeed not have EWS enabled. This was disabled 2 weeks ago but I have not yet received the reason.

Running a backup of the mailboxes after EWS was enabled was successful and they are now once more protected.

Thank you for the information.