GMS has told a remote system to stop sending the message now because the local file system has reported an unexpected error when writing the data to disk. The remote system should try sending the message later when the error may have corrected itself.
In this case, session Undefined is processing a connection from Undefined which was processing email apparently from Undefined for Undefined (if there are multiple receipts for the message, this is the first recipient). GMS has temporarily rejected this message by responding with
The message was being spooled into the local file Undefined and the Operating System responded with an error code of Undefined.
To resolve this issue you should contact Gordano Support. In the meantime, if the problem resolves itself and the remote server complies with Internet Standards, it should hold the message and attempt to resend.
Keywords:temporary reject file system error RFC1870