An existing connection was forcibly closed by the remote host
This error message may occur when migrating a large item (containing large attachments, for instance). The Destination system will keep a connection open only for so long, after which the connection will be closed (timeout).
Mailbox Migration Resolution:
If the destination server's configuration is under your control:
- Increase the connection timeout for incoming data transfers.
- Increase the size limit of items that can be created through the API.
Once the migration completes:
Cannot Retrieve Permissions
Error message
The underlying connection was closed: A connection that was expected to be kept alive was closed by the server.: /personal/leandie_cpgp_co_za/Documents/3D DRAWINGS/Item 4.2 (X-Tech)/M060642063 - 2010-06-02 Rev 1/Smalls Parts/Dwg/p10 - STANDARD.DWG ---> The underlying connection was closed: A connection that was expected to be kept alive was closed by the server. ---> Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host. ---> An existing connection was forcibly closed by the remote host.
Cause
This generally happens in document migrations, specifically Office 365 migrations. This is almost always due to Microsoft throttling.