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BugZero found this defect 301 days ago.
Starting on December 11th, 2023, Exchange backup within Veeam Backup for Microsoft 365 fails with the following errors: There is an error in XML document and The specified type was not recognized: name='SharingMessage'
Veeam has observed that there have been changes to the structure of the XML message received from M365 referencing the SharingMessageType property received from EWS. The Veeam Backup for Microsoft 365 software is unable to process this XML structure. WSL definitions of EWS service can be found here: EWS XML elements in Exchange
The issue is fixed in latest Cumulative Patch for: Veeam Backup for Microsoft 365 7 - Cumulative Patch 7.0.0.4551 (P20231218) Veeam Backup for Microsoft 365 7a - Cumulative Patch 7.1.0.1401 (P20231218)
Veeam R&D Forums Thread: There is an error in XML document