SMTP
Technology & Computing abbreviation · Networking
| Stands for | Simple Mail Transfer Protocol |
|---|---|
| Categories | Technology & Computing |
SMTP stands for Simple Mail Transfer Protocol, a networking abbreviation.
The protocol mail servers use to send and relay email across the internet, and that email apps use to submit outgoing messages. Servers exchange mail on port 25, while clients usually submit on port 587 with authentication.
Example: Password-reset emails stopped sending because the app's SMTP credentials expired.
Usage notes
Defined by Jon Postel in RFC 821 in 1982; the current standard is RFC 5321 (2008). SMTP only sends mail; reading it uses IMAP or POP3. The original protocol had no authentication, which enabled spam and spoofing, later addressed by SMTP AUTH, STARTTLS encryption and SPF, DKIM and DMARC checks. Many residential ISPs block outbound port 25 to stop infected PCs from sending spam.
Related abbreviations
More networking abbreviations
- RTT – Round-trip time
- SAN – Storage area network
- SD-WAN – Software-defined wide area network
- SDN – Software-defined networking
- SFTP – SSH File Transfer Protocol
- SMB – Server Message Block
- SNI – Server Name Indication
- SNMP – Simple Network Management Protocol
- SOA – Start of authority (record)
- SPF – Shortest path first
- SRV – Service (record)
- SSH – Secure Shell