End of socket stream data on Lotus Protector for Mail Security

In this case I was experiencing very strange behavior of Lotus Protector for Mail Security with latest firmware 2.8.1, some emails sent to specific domains were successfully delivered, but from some reason LPfMS was treating those emails as unsuccessfully delivered and were parked into resend queue. The sender was receiving report for temporary delivery error and after few hours a report that maximum number of delivery attempts has been reached, even though the email was successfully received by the email recipient ! Smtp server on LPfMS is based on XMail smtp server.
Following error was logged for those emails:
"End of socket stream data (2) No such file or directory - 417 Temporary delivery error"

I have opened a case for this kind of behavior, and the support engineer has recommended to change the time out value for LPfMS to send the command and to wait for getting the response back from the foreign SMTP server. The default value is 30 seconds. After raising the time out value, this strange behavior of LPfMS was gone. This parameter is smtp.send_dialog_timeoutms and can be set on Mail Security -> Policy -> Advanced Parameters. The parameter is accepting values in milliseconds.  

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