by Colin Cohen | Published on November 13, 2023
Port 995 is dedicated to POP3 using SSL/TLS encryption. This protocol lets email users download messages from an email server using an email client like Outlook or Gmail.
Post Office Protocol Explained
POP3 lets users securely receive email messages over port 995. It works by having an email client communicate with an email server over the port. Once a secure connection is established and the server authenticates the user’s credentials during a POP3 session, the client can receive new messages from the server for that particular user.
Here are the set of commands a client may pass to a server during a POP3 session:
Command | Meaning |
USER [username] | Sends the user’s name. |
PASS [password] | Sends the user’s password. |
QUIT | Quits the session. |
STAT | Receives the number of new messages and their total size. |
LIST | Lists new messages. |
RETR [message ID] | Receives a message. |
DELE [message ID] | Deletes a message from the server. |
TOP [message ID] [lines to return] | Receives the beginning of a message. |
UIDL [message ID] | Receives a message ID. |
NOOP | Receives a response from the server. |
RSET | Undeletes any message that’s been marked for deletion. |
Unlike using POP3 over port 110, POP3 over port 995 requires using SSL/TLS encryption. Both the clients and the server must use the same encryption.
What is POP3?
POP stands for the “Post Office Protocol.” Over the years, there have been many versions of the protocol. POP3 represents the third and most advanced version of it.
How are Secure Socket Layer and POP3 Related?
When you use POP3 over port 995, you must use encrypted communication using SSL/TLS. This prevents the transmission of sensitive information in plaintext, mitigating many vulnerabilities associated with using POP3 over port 110 with unencrypted communication.
How Does Port 995 Work?
Port 995 works by having an email client establish a secure connection with an email server. This connection uses TCP as a transport protocol.
Establishing Connections to Email Servers with POP3
Email clients must establish a secure connection to email servers when using POP3 over port 995. This entails the following handshaking process:
The client notifies the server of the SSL/TLS protocol it wants to use and the encryption technique.
If the server supports the requested protocol and encryption technique, it responds with its digital certificate, which includes its public key.
See AlsoWhat is Port 993?The client verifies the certificate and begins a POP3 session.
How Does POP3S Secure Email Downloads?
The POP3S protocol over port 995 provides for secure email downloads by using SSL/TLS encryption. This means that even if an attacker gains access to a POP3 transmission through a packet sniffer or other means, they cannot access confidential information passed within the transmission.
Is Port 995 POP or IMAP?
You use port 995 when using the POP3 protocol with encrypted communication and port 110 for unencrypted communication. IMAP, which is similar to POP3 but provides more features and better security, uses port 993 for encrypted communication and port 143 for unencrypted communication.
Is Port 995 TCP or UDP?
When using POP3 over port 995, you use the TCP transport protocol. This is because TCP, unlike UDP, provides reliable transfer of commands, responses, and message data.
What are the Differences Between Port 995 and Similar Ports?
There are several ports similar to port 995, which is for the POP3 protocol. This includes ports 143 and 993, which are for the IMAP protocol.
What's the Difference Between Port 995 and 993?
Port 995 and port 993 are both related to securely downloading mail messages from email servers using SSL/TLS encryption. Port 995 is for doing so using the POP3 protocol, while port 993 is for using the IMAP protocol.
Are Port 995 and IMAP Server Port 143 Related?
Port 995 and port 143 are related in that they both facilitate the downloading of mail messages from email servers. While you use port 995 for doing this using the POP3 protocol over an encrypted connection, you use port 143 when using the IMAP protocol over an unencrypted connection.
What is the Default Port Number for IMAP?
The default port number for the IMAP protocol is 143. When using this port, communication between email clients and servers is unencrypted. For encrypted communication using IMAP, you use port 993.
POP3 vs IMAP: Which Email Protocol to Use?
Because IMAP has better security and more features than POP3, such as the ability to keep multiple email clients in sync, you will likely choose it as an email protocol. However, if you only have a single client on a single device, POP3 will work just fine.
What are the Security Concerns and Vulnerabilities with Port 995?
When using POP3 over port 995, you need to ensure you are using the latest version of SSL/TLS. You also need to configure a valid security certificate on port 995.
Weak SSL/TLS Configurations on Port 995
Using older SSL/TLS protocols such as TLS 1.0 or TLS 1.1 can lead to vulnerabilities such as POODLE, BEAST, Heartbleed, and CRIME. You should always use the latest version of the protocol, which is currently TLS 1.3 at the time of publication.
Port 995 and Potential Certificate Issues
Many email services, such as Gmail, will not connect to POP3 servers that do not have a valid SSL certificate from a trusted certificate authority installed on port 995. You need to ensure you have a valid certificate (not one that has been self-signed) and that it has been properly installed on port 995.
Inherent Vulnerabilities with SSL/TLS
Older versions of SSL/TLS are inherently vulnerable to a wide range of attacks. This is why always using the latest version of the protocols is so important.
Danger of Misconfiguring Servers
If you misconfigure your POP3 servers using an outdated encryption protocol, you can open your servers to serious attacks. If you don’t properly configure a valid security certificate, many email services will not connect.
What are Potential Port Overlaps or Conflicts with Port 995?
While port 995 is the standard port for accessing POP3 servers over an encrypted connection, you can use other ports when a conflict arises. But you must then configure all devices that connect to it to use this nonstandard port.
IANA Well-Known Port 995
The Internet Assigned Numbers Authority (IANA) assigned port 995 to POP3 using SSL/TLS encryption. You should probably use this port unless you experience a conflict. In such a case, you can configure your POP3 server to use a different port.
Non-Standard or Misconfigured Ports
If you configure your POP3 server to a different port than 995, you must configure all devices that connect to it to use this nonstandard port. A misconfigured port will lead to users being unable to access new email messages.
Conclusion
You use port 995 to implement the POP3 protocol over an SSL/TLS connection. This allows email clients to securely download mail messages from email servers. While POP3 lacks the features and security of IMAP, many email clients still support it.
