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Port 109POP2

The Post Office Protocol version 2 (POP2) is an early email retrieval protocol designed to facilitate the transfer of email messages from a remote mail server to a local client. Developed in the 1980s, POP2 supports basic operations for listing, retrieving, and deleting messages stored on the server. Despite its historical significance, POP2 has largely been replaced by the more advanced and secure POP3 protocol due to evolving email requirements and the need for enhanced security..

inEmail
transport
tcp

single transport

in transit
cleartext

payload readable on path

assignment
official

registered with iana

risk
4/10

caution

lookups
17,932

rank 150 of 993 · top 15%

Technical Details

what runs on :109

The Post Office Protocol version 2 (POP2) operates primarily over TCP port 109. It was designed as an enhancement to the original POP1 protocol, providing more refined command structures for managing email retrieval. POP2 relies on a client-server model where users authenticate with their credentials, allowing them to connect to their designated mailbox.

POP2 supports commands to list emails, retrieve individual messages, and delete emails on the server. However, POP2 is inherently a simple, stateless protocol—meaning once the emails are fetched, they are typically removed from the server, limiting email synchronization across multiple devices.

With the evolution of email technologies, including the advent of IMAP and POP3, POP2 has become obsolete. The newer protocols offer improved capabilities, such as support for multiple folders, better synchronization, and enhanced authentication methods.

Security Information

exposure of :109

risk score

4/ 10caution

worth attention. how exposed you are depends on configuration — don't leave it reachable from the internet without a reason.

email averages 3.9 across 42 ports — this one sits 0.1 above.

in transit

cleartext

credentials and payloads are readable by anyone on path

assignment

official

registered with iana for this service — scanners fingerprint it by number

reachable over

tcp

every listening transport is another surface to filter at the edge

security overview

Common Vulnerabilities:

  • Lack of encryption in POP2 results in plain-text transmission of emails and credentials, making it susceptible to eavesdropping and man-in-the-middle attacks.
  • Weak authentication mechanisms increase the risk of unauthorized access.
  • Being outdated, POP2 implementations may harbor unpatched vulnerabilities or lack modern safeguards.

Common Mitigations:

  • Replace POP2 with more secure and modern protocols like POP3 over TLS or IMAP with SSL/TLS encryption.
  • Use network encryption mechanisms such as VPNs when legacy POP2 access cannot be disabled.
  • Enforce strong, complex user passwords and monitor authentication attempts to detect misuse.
  • Block TCP port 109 at the network boundary to prevent external POP2 access unless absolutely necessary.

Related Ports

all 42 in email →

the 8 most looked-up other ports in email — 42 ports carry that label.

portservicerisk
:143IMAPcaution
:995POP3Scaution
:2096cPanel SSL Webmailsafe
:110POP3caution
:993IMAPScaution
:1352Lotus Notes RPCcaution
:24Private Mailcaution
:7025Zimbra LMTPcaution

risk mix of the 8 listed

  • safe13%
  • caution88%

3 of 8 encrypted