What is SMTP?

SMTP stands for Simple Mail Transfer Protocol. SMTP is basically the protocol that allows your computer or mobile email app to create and send emails to the server while an API is simply the window or communication to another code or utility.

What is an SMTP Relay?

SMTP Relay is simply described as the method of forwarding E-mails from a sender to the recipient on the Internet; and this process is carried out by the so-called SMTP relay servers, that work in accordance with the Simple Mail Transfer Protocol.


Functions of SMTP Relay Service

  • Smarthost Configuration and Authentication methods include Whitelists, SMTP-After-POP, or ESMTP with the SMTP-Auth extension.
  • Open Mail relay with the SMTP server routes messages from both External sources and Internal server mail making it more vulnerable to spam abuse.
  • SMTP Relay server enables Extensions and Upgrades
  • Parallel Scanners and Firewalls are installed for Fighting spam at the sender’s end.
  • SMTP Relay also Allows Backup Mail service with the Recipient through Smarthost Configuration

Features of SMTP Server You Should Know About

  • Background processing Includes Managing Connections, checking for Errors in Command and E-mail messages, and Reacting accordingly.
  • Persistent SMTP Connection
  • Looping that may result in an E-mail message being passed back and forth between two SMTP servers, each Thinking the other is the Intended Recipient.
  • Have Multiple Processes running on the Same Machine


An SMTP Port refers to the Specific part of the Internet address that’s used to Transfer Email.

  • SMTP port 587 is one of the best choices for nearly every use case for connecting to Pepipost
  • Port 25 is the default port used for Relaying
  • Port 465 should no longer be used at All
  • Port 2525 used when all other port is Blocked

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