Veeam Backup for Office 365 Timeout Errors

KB ID: 2440
Product: Veeam Backup for Microsoft Office 365
Version: All
Last Modified: 2018-02-02


A Veeam Backup for Office 365 job fails with a timeout error.  

These commonly are reported as one of the the following errors:

  • Unexpected End of File
  • Exchange Web Services error code: ErrorExceededConnectionCount
  • Error: Failed to get folder properties
  • Error: You have exceeded the available concurrent connections for your account.  Try again once your other requests have completed.
  • Error: Unexpected end of file has occurred. The following elements are not closed: m:Data, m:ExportItemsResponseMessage, m:ResponseMessages, m:ExportItemsResponse, s:Body, s:Envelope. Line 1, position 21397505.
But are not limited to these errors.



There are multiple causes for these timeout errors.  The most common being a bad connection to the Exchange Web Service (EWS) from the Veeam Backup for Office 365 server or proxy.  This can be caused by a flooding of open worker threads to the Exchange Web Services server, network traffic saturating the throughput of the connection, a slow internet connection to the Office 365 EWS server amongst other issues.


In 1.5, performance settings to help with timeout errors can be adjusted through the proxy performance settings (Concurrent Threads, and limit network bandwidth).  If adjustment of these performance settings still cannot resolve the timeout errors, we can modify the Proxy.XML data (found by default at %programdata%\Veeam\Backup365\) by adding the following information into the XML document under <source>:

<Source BatchSize=”100” BatchPart= “100” BatchTimeout= “600” BatchMaxItemSize=”256” />

Keys explanation (default values):
•    BatchSize (100) - Maximum number of items requested from EWS (Exchange Web Services) per one query
•    BatchPart (100) – Should be set the same as the BatchSize at this moment
•    BatchTimeout (600) - Timeout for getting a reply with results from EWS in seconds
•    BatchMaxItemSize (256) - Maximum size of an item (in MB) requested from EWS per one query. If the item size exceeds BatchMaxItemSize, item will be requested separately
In 1.0, these performance settings would need to be configured in the Config.xml file (found by default at %Programdata%\Veeam\Backup365).


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