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Info: Using Telnet to Test a POP3 Connection


Product: ModusMail

Version & Build: All


Telnet commands can be used to test POP3 connections to the mail server to test if you can successfully open a POP3 session on the server and if you can properly authenticate a valid email address.

Below isthe standard syntax used for the telnet commands:


Example:  The POP3 connection for is configured on IP, port 110.
On the ModusMail server, open a DOS command window (e.g., Start > Run > cmd):

1.Use the telnet command to open a connection to the mail server, e.g. type: telnet 110 <Enter>'

Note: if using Windows 2000, you may want to use the following set of commands to turn the local echo function on and display what you're typing. Local echo is enabled on Windows 2003 and XP by default.

    • From the DOS prompt, type telnet <Enter>
    • Type set local_echo <Enter>
    • Type open 110 <Enter>

2. Important note - telnet does not allow backspaces so, if you make a mistake when entering the commands, start over.

3. When the telnet screen opens, you should see the mail server's banner, similar to: 
OK MailServer POP3 Server 4.2.420.0 Ready
(If you don't get a banner, check the IP address and firewall configuration and start the test again)

4. Type user followed by a valid username, e.g. user mailboxname <Enter>

5. The mail server should reply: OK ...

6. Type pass followed by the mailbox password, e.g. pass mailboxpassword <Enter>

7. If the mail server reply is OK, you have successfully logged into the Email server using the POP3 protocol 

8. If the mail server reply is invalid mailbox or password, you may have the wrong password (or mistyped it) or the domain is set up as a virtual domain, meaning it does not have a unique IP address.  In this case you must enter the full email address as the username.  Without closing the telnet screen, do the following:

  • Type user with the full email address, e.g. user <Enter>
  • Type pass followed by the mailbox password, e.g. pass mailboxpassword <Enter>
  • If the mail server reply is OK, you have successfully logged in

9. If the server replies that you have multiple messages in the mailbox, you can enter the list command to display the sizes of the individual messages.

10. To see the content of a specific message,type retr (retrieve) and the message number, e.g. to see message # 3, type retr 3 <Enter>.  The content of the message, including header information, is displayed in text format.

11. To delete a message, type dele with the message number, e.g. dele 2 <Enter>

12. End the telnet session by typing quit <Enter> to end the POP3 communication

Here are the same transactions on screen:
>Telnet 110
+OK ModusMail POP3 Server 4.2.420.0 Ready <>
>user mailboxname
+OK mailboxname is welcome here
+OK mailboxname's mailbox has 3 message(s) (4544 octets)
+OK 3 messages (4544 octets)
1 343
2 2123
3 2078
dele 2
+OK message 2 deleted
+OK POP3 server signing off (2 messages left)
Modified 12/20/2006
Keywords: telnet pop3
Article ID: 1416