12 February 2017

How to test a POP server by using telnet

What you need

  • The host name of the POP server (for use in the telnet command)
  • The POP user name (for use in the USER command)
  • The user’s POP password (for use in the PASS command)

Encryption

For added security, you can encrypt your POP connection. This requires that your server supports SSL or TLS and that you have access to an SSL/TLS client program, for example OpenSSL, to use instead of telnet.

As the port number normally is 995, an example OpenSSL command would be openssl s_client -connect pop.example.com:995 -quiet. (If you would like to see the public key of the server, as well as some other encryption-related information, omit -quiet.) The server should then start a POP session, displaying a greeting such as the +OK InterMail POP3 server ready example below.

What to do

The DELE command flags messages for deletion. Use it only if you want to delete mail.

The initial telnet: > symbolises your shell prompt.

telnet: > telnet pop.example.com pop3
telnet: Trying 192.0.2.2...
telnet: Connected to pop.example.com.
telnet: Escape character is '^]'.
server: +OK InterMail POP3 server ready.
client: USER MyUsername
server: +OK please send PASS command
client: PASS MyPassword
server: +OK MyUsername is welcome here
client: LIST
server: +OK 1 messages
server: 1 1801
server: .
client: RETR 1
server: +OK 1801 octets
server: Return-Path: sender@example.com
server: Received: from client.example.com ([192.0.2.1])
server:        by mx1.example.com with ESMTP
server:        id <20170120203404.CCCC18555.mx1.example.com@client.example.com>
server:        for <recipient@example.com>; Fri, 20 Jan 2017 22:34:24 +0200
server: From: sender@example.com
server: Subject: Test message
server: To: recipient@example.com
server: Message-Id: <20170120203404.CCCC18555.mx1.example.com@client.example.com>
server: 
server: This is a test message.
server: .
client: DELE 1
server: +OK
client: quit
server: +OK MyUsername InterMail POP3 server signing off.