Exploring a POP3 Server Over Port 110 Using the Terminal
Once you have a connection to a POP3 server over Port 110, you can do a lot more than just check if the port is open — you can actually explore the server, see what mail software („mailer“) it’s running, and even check if there are any messages in the mailbox.
Here’s how:
1. See the Mail Server („Banner“)
When you connect with:
nc serveraddress 110
the server will immediately greet you with a „banner“ message.
Examples might be:
+OK Dovecot ready.
or
+OK Microsoft Exchange POP3 service ready
This banner often reveals which mail software (like Dovecot, Courier, Cyrus, Exchange, etc.) is running.
2. Explore the Server
After connecting, you can type:
CAPA
to request the server’s capabilities.
You’ll get a list of supported features like TOP, UIDL, AUTH methods, and sometimes even hints about the mail system.
3. See if Mails Are in the Inbox
To check for messages after logging in:
First, authenticate:
USER yourusername
PASS yourpassword
Then, use:
STAT
which returns the number of messages and their total size.
Or:
LIST
to get a detailed list (message numbers and their sizes).
If you want to view a message:
RETR 1
to retrieve the first email.
You can also delete a message by:
DELE 1
(be careful: DELE marks the message for deletion — it’s only actually deleted after you send QUIT.)
4. Most Useful POP3 Commands at a Glance 🚀
Command: USER — Purpose: Send your username
Command: PASS — Purpose: Send your password
Command: STAT — Purpose: Show number of emails and size
Command: LIST — Purpose: List all emails with their sizes
Command: RETR — Purpose: Retrieve the full email number n
Command: DELE — Purpose: Mark email number n for deletion
Command: QUIT — Purpose: Log out and end the session
With just these few commands, you can fully inspect a POP3 mailbox manually without any mail client!
5. Exit the Session
After retrieving a mail with RETR 1, just watch for a single line with a period (a simple dot „.“) — this marks the end of the message.
Once you see the „.“, you can immediately continue sending commands like QUIT to end the session.
No special action needed to exit out of message view.
6. Useful Keyboard Shortcuts in Terminal
If anything hangs or gets stuck:
CTRL + C — Immediately abort the current operation
CTRL + D — Send EOF (End of File), cleanly end input
CTRL + ] — Escape telnet sessions
CTRL + Z — Suspend the process (send it to background)
Tip:
If you feel stuck during a nc or openssl session, just press CTRL + C — you’ll jump straight back to your terminal without any trouble. 🎯