Patent ID: 7369258

Claim:
A network communication device, comprising: response verification means for, over a network, making a request to a transmission destination being a receiving-end terminal to return a response and verifying that the response has been made within a predetermined waiting time; measuring means for measuring a response time from the making of the request to reception of the response, the response time being set in an MDN function to verify the response from the receiving-end terminal, and an email transmitted to the receiving-end terminal is determined as being undelivered if no response from the receiving-end terminal is verified within the response time; and changing means for changing the waiting time in accordance with a result of the measurement by the measuring means, wherein the changing means, if the response time has been previously measured more than once, designates as the waiting time a mean response time of measured response times, exclusive of a maximum value and a minimum value thereof, with an adjustment time added to the mean response time.