Testing POP3 service using a telnet session]
It is possible to telnet to Port 110 on a server offering a POP service for users to collect their mail. The telnet test is useful for testing a number of POP server related features.
1) Ensuring that the POP server is responding to requests as expected on port 110
2) Testing that a local user account can authenticate correctly
3) Checking the size of mail items, and total size of mail in a user Inbox
4) Checking the total number of items in a users Inbox
The test conducted below was achieved using the Exchange 2007 POP service.
NOTE: With a telnet session you cannot use the backspace or delete keys. If you mistype a command you will need to retype the whole command again after receiving an error. Too many errors and the telnet session will automatically close and you will need to start again.
Open a command prompt and type telnet [servername] 110 to start the telnet session on the POP server.
You should receive a message stating that the POP server is ready to accept commands.
Provide your username. This can be in the form [username] / [username@localdomain] or other formats depending on the authentication format acceptable to the pop server.
Provide your password. This will display in clear text so be careful who if looking over your shoulder!
You can use a variety of command now you have successfully authenticated. One such command is STAT. This command will give you a figure to represent the amount of messages in the inbox, and then a second figure representing the size in bytes of the whole inbox.
Another command is LIST. This will show you a list of all the messages in the Inbox. The figure next to it is the total size in bytes.
The RETR command requires a parameter (the number representing the message). So RETR 7 will retrieve the seventh message. You can use this command to type the RAW email message in plain text. Note that HTML processing and MIME type data will appear just as plain text and may appear garbled but this is expected and normal.
The DELE command will delete the message you specify. You should use this command with care, as you are deleting messages from the Inbox.
And the final command is QUIT, which as expected will end the telnet session.
That concludes this article on testing POP3 with telnet.
Please review these external links for further information regarding testing POP3 with telnet:
Thank you for your comment. Good point about mobile devices, I will try to remember to include full text based representation in future articles.
For clarifications here the user command is USER [USERNAME]. Password command is PASS [PASSWORD] and Delete command is DELE [NUMBER IS OF MESSAGE TO DELETE].
Diagnosing POP3, IMAP and SMTP via SSL