September 30, 2020
2 min read
Simple Mail Transfer Protocol (SMTP) is a set of guidelines to send emails across the internet.
This protocol is configured by a mail client – a desktop application that manages emails – to make sure the email messages get delivered to the right recipient.
SMTP uses Transmission Control Protocol (TCP), a connection-oriented protocol which guarantees successful email delivery.
There are two types of SMTP models:
These are the standard transmission channels used by SMTP to transmit email messages:
An SMTP server is a program that runs SMTP. It’s also known as an outgoing email server.
SMTP servers have addresses set by the mail clients or email providers. These are usually formatted as smtp.serveradress.com.
For instance, Yahoo! Mail’s STMP server address is smtp.mail.yahoo.com, while Gmail uses smtp.gmail.com.
Since an outgoing mail server can only send a limited number of emails, many businesses that run an email marketing campaign or send thousands of transactional messages every day choose to use SMTP service providers.
SMTP services are third-party applications that ensure you have a secure SMTP relay for fast and reliable email deliverability.
An email message needs to be transformed into a set of code before it is sent. Mail clients use SMTP to do the transformation process.
SMTP can only transform plain text into code. Because of this, it works together with Multipurpose Internet Mail Extensions (MIME) to encode non-text content like fonts, graphics, attachments, and so on.
After encoding the email message, SMTP will transfer the code to an SMTP server.
It will then verify the code to confirm that the message is legitimate. It will also check the recipient’s email address by looking for its domain located in the Domain Name System (DNS).
For instance, if you’re sending a message to firstname.lastname@example.org, the SMTP server will locate ymail.com and transfer the email to that specific destination.
Once the encoded email arrives in the recipient’s mail server, it will be converted into a human-readable message by either POP3 or IMAP protocol ‒ both of which are protocols for receiving emails.