MAPI Automatically Disabled Constantly

Question

MAPI Automatically Disabled Constantly

Harry Stenson 0

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Outlook desktop (MAPI) is disabled in all except one of the usermailboxes in a tenant we manage. This happens every time I check following some time (typically overnight) after enabling these mailboxes.

These users are unable to utilise Outlook Classic when MAPI is disabled.

Is there any suggestions as to what's disabling this? I've bashed my head against a wall for collective hours trying to figure it out. Audit logs are not providing any indication whatsoever, and anything it has suggested such as SaaS Alerts has been unhelpful.

Vergil-V 12,975 Reputation points Microsoft External Staff Moderator

2026-05-18T11:47:30.69+00:00
Hi @Harry Stenson

I can understand how this behavior may feel unexpected, as the scenario is quite unique compared to what we usually see. Based on my research, I would like to suggest some steps that may help you investigate further.

1/ Verify Current MAPI Status via PowerShell

First, please confirm the MAPI status using PowerShell and compare it with what you see in the Admin Center UI. This will help ensure the setting is consistent across both views.

Get-CASMailbox -ResultSize Unlimited | Select-Object DisplayName, PrimarySmtpAddress, MAPIEnabled

2/ Check the Mailbox Plan

Kindly review the mailbox plans and check if any plan has MAPIEnabled set to False, as this may affect how the setting is applied to users.

Get-MailboxPlan | Format-List DisplayName, MAPIEnabled

3/ Compare the affected user with an unaffected user

It would be helpful to compare the affected user with another user who is not experiencing this behavior. Please review areas such as licensing, mailbox plan assignment, and related configurations to identify any differences.

4/ Search Audit Logs for MAPI changes in the past week

You can also review audit logs to check whether there were any recent changes related to MAPI settings. Looking at activities from the past 7 days may provide more context.

Search-UnifiedAuditLog -StartDate (Get-Date).AddDays(-7) -EndDate (Get-Date) -Operations "Set-CASMailbox" -ResultSize 5000 | Select-Object CreationDate, UserIds, Operations, AuditData | Format-List

I hope these steps provide some helpful direction. If you have any updates after reviewing them, please feel free to share.

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