Email Ports: SMTP (25/587), IMAP (143/993), POP3 (110/995)
Complete reference for email protocol ports. SMTP ports 25 and 587, IMAP ports 143 and 993, POP3 ports 110 and 995. Learn which port to use for secure email.
Detailed Explanation
Email Protocol Ports
Email relies on several protocols, each with encrypted and unencrypted variants. Choosing the right port is essential for reliable and secure email delivery.
SMTP — Sending Email
| Port | Use | Encryption |
|---|---|---|
| 25 | Server-to-server relay | None (STARTTLS optional) |
| 465 | Submission (legacy) | Implicit TLS |
| 587 | Submission (recommended) | STARTTLS required |
Port 25 is used for server-to-server mail relay (MTA-to-MTA). Most ISPs block outbound port 25 from residential connections to prevent spam. Port 587 is the recommended port for email clients submitting mail to their SMTP server, using STARTTLS for encryption. Port 465 was briefly assigned for SMTPS but was deprecated, then re-standardized in RFC 8314.
IMAP — Retrieving Email (Server-side Storage)
| Port | Encryption |
|---|---|
| 143 | None (STARTTLS optional) |
| 993 | Implicit TLS |
IMAP keeps emails on the server and synchronizes across devices. Port 993 with TLS is the standard for modern email clients.
POP3 — Retrieving Email (Download and Delete)
| Port | Encryption |
|---|---|
| 110 | None (STARTTLS optional) |
| 995 | Implicit TLS |
POP3 downloads emails to a local client and typically deletes them from the server. Port 995 with TLS should always be used.
Which Port Should I Use?
- Sending mail from an application: Port 587 with STARTTLS
- Checking mail with a client: Port 993 (IMAP) or 995 (POP3)
- Running a mail server: Accept on port 25 for incoming relay, 587 for client submission
Use Case
Configuring an email client or application to connect to a mail server using the correct ports with TLS encryption for both sending (SMTP) and receiving (IMAP/POP3) messages.
Try It — Port Number Reference
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