Subnet and PortsEmail ports: 25, 465, 587, 110, 143, 993 and 995
What the IANA registry records for these ports, and how to use them safely.
What IANA records
| Port | Protocols | Registered name | IANA description | Assignee | Reference | Note |
|---|---|---|---|---|---|---|
| 25 | tcp, udp | smtp | Simple Mail Transfer | IESG | [RFC-ietf-emailcore-rfc5321bis-43] | |
| 465 | tcp | urd | URL Rendezvous Directory for SSM | Toerless Eckert | n/a | |
| 465 | tcp | submissions | Message Submission over TLS protocol | IESG | [RFC 8314] | |
| 465 | udp | igmpv3lite | IGMP over UDP for SSM | Toerless Eckert | n/a | |
| 587 | tcp, udp | submission | Message Submission | n/a | [RFC 6409] | |
| 110 | tcp, udp | pop3 | Post Office Protocol - Version 3 | Marshall Rose | n/a | |
| 995 | tcp, udp | pop3s | POP3 over TLS protocol | IESG | [RFC 8314] | |
| 143 | tcp | imap | Internet Message Access Protocol | IESG | [RFC 3501]; [RFC 9051] | |
| 993 | tcp | imaps | IMAP over TLS protocol | IESG | [RFC 3501]; [RFC 8314]; [RFC 9051] |
Sending and receiving use different ports
Email programs use one set of ports to send mail and another to fetch it.
- Sending to a mail server from your mail program (submission): 587 is the standard submission port (registered as
submission). 465 is registered assubmissionsin current IANA data, for submission with TLS from the start. - Server to server (SMTP): 25. This is how mail servers pass mail to each other. Many providers block outgoing port 25 from ordinary home connections to limit spam.
- Fetching mail: IMAP keeps mail on the server and lets several devices share it (143 plain, 993 with TLS). POP3 downloads mail (110 plain, 995 with TLS).
Which to choose in your mail settings
| Job | Port | Security setting |
|---|---|---|
| Send | 587 | STARTTLS, or 465 with SSL/TLS |
| Receive, IMAP | 993 | SSL/TLS |
| Receive, POP3 | 995 | SSL/TLS |
Use the encrypted ports. Plain 110 and 143 send passwords and mail in the clear unless the server upgrades the connection.
Safe habits
- Always turn on encryption for sending and receiving.
- Use an app password or two-step verification where the provider supports it.
- If sending fails, check that your provider allows the port you chose; some networks block 25 and 465.
- On a server, close ports that you do not use; an open mail relay on port 25 is quickly abused.
This is an independent guide. It is not connected with IANA, the IETF or any network equipment maker. Address and port data come from the IANA registries as fetched on 14 November 2026; RFC texts were read from rfc-editor.org. Check the originals for anything you rely on.