Telnet is a protocol designed to remotely access computers in a client-server fashion. Telnet is inherently insecure, as the data passed from the client to the server or vice-versa is not encrypted. For connections through insecure networks (such as the Internet), SSH (Secured SHell), should be used so all communications between the client and server are encrypted.
Test if the HTTP port is open and its service listening
telnet localhost 80
Send an email
telnet localhost 25 Trying 127.0.0.1... Connected to localhost.localdomain. Escape character is '^]'. 220 smtp.mydomain.com mail from:<email@example.com> 250 2.1.0 <firstname.lastname@example.org>... Sender ok rcpt to:<email@example.com> 250 2.1.5 <firstname.lastname@example.org>... Recipient ok data 354 Enter mail, end with "." on a line by itself Let's meet . 250 2.0.0 n514OvkN019941 Message accepted for delivery quit 221 2.0.0 smtp.mydomain.com closing connection Connection closed by foreign host.