This article applies to:
Exchange Hybrid deployment
User receives “unable to expand folders” error in Outlook 2016 when opening a mailbox that has been moved to Office 365.
Although the mailbox switchover may be reported as successfully completed, if you check the log for the mailbox, in the mailbox migration batch, it may contain one or multiple entries as following:
15/11/2016 17:05:35 [VI1PR0901MB0974] A corrupted item was encountered: Unable to translate principals to the target mailbox: Failed to find a principal in the target forest that corresponds to a source forest principal.
15/11/2016 17:05:35 [VI1PR0901MB0974] A corrupted item was encountered: Unable to translate principals to the target user: Failed to find a principal in the target forest that corresponds to a source forest principal.
The problem occurs if permissions list on the mailbox contains an Active Directory user that is disabled or does not exist any more.
Disabled or deleted user accounts will not be replicated to Office 365 and therefore will cause problems with permissions processing as the entries in the mailbox permission lists cannot be mapped to a valid user in Office 365.
This can also occur when the Outlook auto mapping feature tries to automatically open another mailbox to which user has Full Mailbox Permissions, but the target mailbox has the mentioned problem with non-existing users on the permission list.
Login to the Office 365 Exchange Admin center . Under Recipients / Mailboxes, select the affected mailbox and open its Properties.
Under Mailbox Delegation check all the permissions and remove any non-existing or disabled users.
He lives in Zurich, Switzerland and is a dedicated specialist, with 30 years of professional work experience in IT.
Before starting Exchangemaster GmbH he worked as a system engineer and project manager with customers of all sizes and across many industries: From small ISV startups and a NGO humanitarian organizations up to largest international corporations like Stryker, Swisscom, British Telecom and Nyrstar.
He spent his entire career delivering Microsoft based infrastructure solutions with main focus on Active Directory and Exchange. During those years, he collected a valuable work experience on 8 Exchange generations (2019, 2016, 2013, 2010, 2007, 2003, 2000 and 5.5) and has delivered services to a user base of more than 3.2 million mailboxes in on-premise, hybrid and Office 365 deployments.
Beside working on customer projects, he is a regular speaker and expert at Microsoft conferences and user groups. As a Microsoft Certified Trainer he also teaches Microsoft Official Curriculum courses to technical professionals around Europe.
For his work he has received numerous awards.
In 2005 he was the first member to be elected into the MCP Hall of Fame by Windows IT Pro Magazine readers choice (as 1 of 6 worldwide).
From 2005-2017, Dejan has been awarded by Microsoft Corporation with the yearly Microsoft Most Valuable Professional award in area of Exchange for 12 years in a row (one of approximately 100 worldwide and, at the time, the only 1 such in Switzerland).
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