Network I/O Error 64 in state 3 This is a low priority error. There are no reported instances of problems in MailSite aside from the sporadic log in the event viewer. Changing MailSite Error Logging to log the File Log or turning off the logging completely will alleviate the number of entries to the NT Event Log. Network I/O error 64 (0X00000040) in state3 encountered in connection with IP address. What cause's this error is when an SMTP connection terminates, it is to follow a sequence. When that sequence gets interrupted it results in this error. Error 64 is what the server sees when an SMTP client sends out the quit command, but does not wait to get the quit response back before it disconnects. "State 3" means that the server was in the middle of sending the quit response when it discovered the connection was already gone.