2 min read Sep 26, 2026

What Is SMTP? A Simple Guide to Outgoing Email

SMTP is the protocol that sends email. Learn what it does, how it works with IMAP and POP3, which ports it uses and the SMTP settings for FimuroHost mail.

FimuroHost Team

FimuroHost Team

Technical Writer

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SMTP (Simple Mail Transfer Protocol) is the standard internet protocol for sending email. Almost every email system in the world uses it to move messages from one place to another.

What SMTP does

  • From your app to your mail server: when you click Send in Outlook, Apple Mail or on your phone, the app hands the message to your outgoing (SMTP) server.
  • Between mail servers: your mail server then uses SMTP to pass the message on to the recipient's mail server, which it finds using the recipient domain's MX records.

SMTP only sends. To read the email in your mailbox, your app uses a separate protocol — IMAP (recommended) or POP3. That's why email apps ask you for both an incoming and an outgoing server.

SMTP ports

PortUsed for
25Server-to-server delivery. Many internet providers block it for home and mobile users to reduce spam.
587Sending from email apps, secured with STARTTLS. The usual choice.
465Sending from email apps over an encrypted SSL/TLS connection.

Your FimuroHost SMTP settings

SettingValue
Outgoing serversmtp.stackmail.com
Port and security587 with STARTTLS, or 465 with SSL/TLS
AuthenticationRequired – your full email address and mailbox password

Good to know

  • Always enable "outgoing server requires authentication" in your app; unauthenticated sending is refused.
  • Sending limits apply per mailbox. See our guide to email sending limits for the current figures.
  • SPF, DKIM and DMARC records help receiving servers trust the mail you send over SMTP.

Need help?

If something doesn't work as described, our team is happy to take a look. Open a support ticket or message us on WhatsApp at 01818160926.

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FimuroHost Team

Written by

FimuroHost Team

Technical Writer