---
title: What is SMTP
description: "**SMTP** stands for **Simple Mail Transfer Protocol**. **SMTP** is used when email is delivered from an email client, such as Outlook Express, to an email server or when email is delivered from one email server to another. **SMTP** uses port 25."
url: "https://support.bluspider.com/kb/what-is-smtp/"
updated: "2024-08-09"
category: Email
---

# What is SMTP

**SMTP** stands for **Simple Mail Transfer Protocol**. **SMTP** is used when email is delivered from an email client, such as Outlook Express, to an email server or when email is delivered from one email server to another. **SMTP** uses port 25.