Answer
GMS was in the process of accepting a message from a remote server when the remote server suddenly started sending empty packets. Empty packets usually mean that there has been either an error at the sending server (although in some cases the remote server may recover) or due to some form of attack. GMS will allow a limited number of empty packets to be sent before disconnecting so that server resources are not used by any form of attack. If the remote server supports RESTART, then when the remote server starts to send the message again it will only send the additional portion of the message rather than the whole message again.
In this case, session Undefined was receiving a message from Undefined when the connection was disconnected because over Undefined empty packets were received.
This is not a problem with Gordano software. Usually, the remote server will connect again and restart or continue to send the message at a later date. However, if this error is occuring due to a large message over a slow connection, RESTART is essential to ensure efficient and eventual delivery of the message so it may be beneficial to contact the owner of Undefined and suggest they upgrade to a server that supports the ESMTP option RESTART.
See Also:
Keywords:Restart disconnect retry checkpoint RFC1845 8132