SMTP (Simple Mail Transfer Protocol) is the standard communication protocol used for sending and relaying email messages across the internet. When you click "send" on an email, SMTP is the technology that handles the entire delivery process from your email client to the recipient's inbox.

The process works in a series of steps:

• Submission: Your email client (like Outlook or Gmail) connects to your email provider's SMTP server using authentication.
• Relaying: The SMTP server looks up the recipient's domain (the part after the @ symbol) using DNS MX records to find the destination mail server.
• Delivery: Your provider's SMTP server communicates with the recipient's mail server and transfers the message.
• Receiving: The recipient's server places the email in their mailbox, where it can be retrieved using protocols like POP3 or IMAP.

For web hosting customers, understanding SMTP is crucial because it affects email reliability and deliverability. Most hosting plans include SMTP services, allowing you to send emails from your website (like contact forms, order confirmations, or newsletters) directly through the hosting server. Proper configuration prevents your emails from being marked as spam.

Key SMTP settings you'll often encounter include the server address (often something like smtp.yourdomain.com or your hosting provider's server), port number (common ones are 25, 465 for SSL, and 587 for TLS), and authentication requirements (your email username and password). Using the correct encrypted ports (465 or 587) is essential for security, as they protect your login credentials and email content during transmission.

If your website emails are not sending, the issue is typically related to SMTP configuration. Always double-check your server settings, port numbers, and login credentials. For high-volume sending (like marketing campaigns), consider using a dedicated transactional email service that specializes in SMTP delivery to ensure maximum inbox placement.