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).
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 mailbox's migration completes:
Enable subject logging of failed items
Retry failed items