Email SMTP - How Online Email Services Crank It Out | Email SMTP Relays Explored
Simple Mail Transfer Protocol - aka SMTP, is the simplest way an email can be sent from one email provider to another. It is one of the cleanest ways emails exchange on Internet mail servers. Typically to use a SMTP service for your email, you will need a mail client like Microsoft Outlook or Mozilla Thunderbird as a platform to send and receive.
It may seem easy once you press the send button on your composed email, but that one little action send quite the process in just seconds as your email jumps from one mail server and routes the path all the way to your recipient. SMTP talks on port 25 in the email spectrum through a couple of SMTP specific methods like HELO and EHLO.
HELO and EHLO are more or less the way SMTP shakes hands on each side of the aisle of a mail server and exchanges information that helps the email address travel through cyberspace and be accepted at the receiving mail server so whomever is in your "To" field will actually get to read your email instead of it being sent back as a "failed delivery" or "give up" as it is better known. HELO is pretty much a shortened version for exactly what it sounds like, and is a protocol for these mail servers exchanging emails to do what we humans do when meeting each other as a "Hello".
Email servers are configured differently, but these settings are typical to most configurations found on business email systems in hospitals, lawyer offices, and other types of corporate mail providers. SMTP is also one of the easiest ways email verification can be performed when trying find out more about an email address. With is being so easy to send through SMTP, it can also be very easy to trace and verify an email in the same manner.