Email protocols and ports
Email ports are communication endpoints that define how a message should be transmitted. This includes whether a message should be encrypted and exchanged securely. To establish a connection between your email client and your mail server, you need its IP address and a port number. Here are some of the most common mail ports:
| Protocol | Port | Security | Description |
|---|---|---|---|
| SMTP | 25 | Non-secure | Used for sending email between servers (unencrypted) |
| POP3 | 110 | Non-secure | Used for retrieving email from a server (unencrypted) |
| IMAP | 143 | Non-secure | Used for retrieving email from a server (unencrypted) |
| SMTP | 465 | Secure (SSL) | Used for sending email between servers (encrypted) |
| SMTP | 587 | Secure (StartTLS) | Used for sending email between servers (encrypted) |
| IMAP | 993 | Secure (SSL) | Used for retrieving email from a server (encrypted) |
| POP3 | 995 | Secure (SSL) | Used for retrieving email from a server (encrypted) |
A) Non-encrypted ports
Port 25 (SMTP): Port 25 is open for Simple Mail Transfer Protocol (SMTP) services and is used for e-mail relay.
The vast majority of today's mail servers use this protocol. When you send an email to someone, a dynamic port on your computer (greater than 1024) connects to port 25 on the mail server, and the email you send is transferred to the mail server and stored there.
B) Encrypted port:
Port 465 (SMTP SSL): Port 465 is open to the protocol service SMTP SSL (SMTP-over-SSL), a variant of the SMTP protocol based on the SSL security protocol, which adopts the high security reliability of the asymmetric encryption of the SSL security protocol to prevent email leakage.
SMTPS is also used to send email like SMTP protocol, but it is more secure, prevents email interception and leakage by hackers, and can also realize the email sender's anti-repudiation function. It prevents the sender from deleting sent messages after they have been sent, and refuses to acknowledge that such a message has been sent.
Receiving protocols and ports
A) Non-encrypted ports
Port 143 (IMAP): Port 143 is open for IMAP service (INTERNET MESSAGE ACCESS PROTOCOL) and is used for receiving e-mails.
Port 110 (POP3): Port 110 is open for POP3 (Post Office Protocol Version 3) service and is used for receiving emails. Many mailbox providers abbreviate it as pop without adding the 3 (e.g. pop.gmail.com).
Port 109 (POP2) – Obsolete: Port 109 is open to POP2 (Post Office Protocol version 2) services and is used to receive e-mail.
What is the difference between IMAP and POP3?
The POP3 protocol allows an email client to download messages from the server, but the client's actions (e.g. moving messages, marking them as read, etc.) are not reported back to the server.
The IMAP protocol allows bi-directional communication between webmail and email clients, and the client's actions are reported back to the server, and the actions performed with the email are also performed on the server accordingly.
B) Encrypted ports
Port 993 (IMAP SSL): Port 993 is open for IMAP SSL (IMAP-over-SSL) protocol services, a variant of the IMAP protocol based on the SSL security protocol, which adopts the high security reliability of the asymmetric encryption of the SSL security protocol to prevent the outflow of emails.
IMAPS is also used to receive e-mail, like the IMAP protocol, but is more secure and prevents e-mail from being intercepted and leaked by hackers, and can also provide anti-rejection features for e-mail recipients. Prevent recipients from deleting received messages after they are received, and refuse to acknowledge receipt of such a message.
Port 995 (POP3 SSL): Port 995 is open for POP3-SSSL (POP3-over-SSL) protocol services, a variant of the POP3 protocol based on the SSL security protocol, which adopts the high security reliability of asymmetric encryption of the SSL security protocol to prevent email leaks.
Like POP3 protocol, POP3S is also used to receive emails, but it is more secure and prevents emails from being intercepted and leaked by hackers, and can also realize the anti-repudiation function of the email recipient. Prevent recipients from deleting received messages after receiving them and refusing to acknowledge the receipt of such message.
Examples of popular services mail protocols and ports:
1. Outlook:
IMAP server name: outlook.office365.com
IMAP port: 993
IMAP encryption method TLS
POP server name: outlook.office365.com
POP port 995
POP encryption method TLS
SMTP server name: smtp-mail.outlook.com
SMTP port 587
2. Gmail:
| Incoming Mail (POP) Server |
Requires SSL: Yes Port: 995 |
| Outgoing Mail (SMTP) Server |
Requires SSL: Yes Requires TLS: Yes (if available) Requires Authentication: Yes Port for TLS/STARTTLS: 587 |
3. TOM Email:
POP3 server address: pop.tom.com (port: 110), encrypted port using SSL: 995 SMTP server address: smtp.tom.com (port: 25), encrypted port using SSL: 587 or 465
4. Yahoo Mail:
- IMAP server name:
imap.mail.yahoo.com - IMAP port: 993
- IMAP encryption method: SSL
- POP server name:
pop.mail.yahoo.com - POP port: 995
- POP encryption method: SSL
- SMTP server name:
smtp.mail.yahoo.com - SMTP port: 465 or 587
- SMTP encryption method: SSL or TLS (if available)
5. Zoho Mail:
- IMAP server name:
imap.zoho.com - IMAP port: 993
- IMAP encryption method: SSL
- POP server name:
pop.zoho.com - POP port: 995
- POP encryption method: SSL
- SMTP server name:
smtp.zoho.com - SMTP port: 465 or 587
- SMTP encryption method: SSL or TLS (if available)
6. ProtonMail:
- IMAP server name:
imap.protonmail.com - IMAP port: 993
- IMAP encryption method: SSL/TLS
- SMTP server name:
smtp.protonmail.com - SMTP port: 465 or 587
- SMTP encryption method: SSL/TLS
7. FastMail:
- IMAP server name:
imap.fastmail.com - IMAP port: 993
- IMAP encryption method: SSL/TLS
- POP server name:
pop.fastmail.com - POP port: 995
- POP encryption method: SSL/TLS
- SMTP server name:
smtp.fastmail.com - SMTP port: 465 or 587
- SMTP encryption method: SSL/TLS
8. GMX Mail:
- IMAP server name:
imap.gmx.com - IMAP port: 993
- IMAP encryption method: SSL
- POP server name:
pop.gmx.com - POP port: 995
- POP encryption method: SSL
- SMTP server name:
mail.gmx.com - SMTP port: 465 or 587
- SMTP encryption method: SSL or TLS (if available)
By configuring your email client with the appropriate server names, ports, and encryption methods for these popular email services, you can ensure secure and efficient email communication.
Final words
Understanding common mail ports and their purposes is essential for secure and efficient email communication. By using the appropriate ports and protocols, you can ensure that your emails are transmitted securely and reliably.
