To provide a communication apparatus by which an erroneous server information is rapidly discovered and corrected when a user inputs it.

A parameter is inputted from an operating part 115 and an IP address, a net mask and a default gateway are set (S371, S372 and S373). After a mail server is set (S374), the mail server is checked (S375). When the mail server is checked, connection is tried to the actually set main server and it is judged that connection is established or not. Whether OK or not is judged as a result of the check (S376). When an error occurs and there is mistake in an inputted server name, for example, warning is displayed in the operating part (S337). A user is reported that usage is not allowed through the user of the inputted name at present by warning display. In the case of OK as a result of checking, the mail server is registered (S38).