How Email Works: The Technical Side of Email Delivery

January 7, 2019

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Email marketing is as strong as ever, and the standard of quality is extremely high for businesses to stay competitive. Even if you consider yourself an expert at email terminology, there’s a chance you’re still unclear about the technicalities of getting an email from Point A to Point B.

Keep reading to learn (or refresh your memory) about exactly how email works. We hope you walk away with a deeper understanding of email delivery mechanisms that will help you become a more informed email marketer.

Understanding Email Servers

The procedure that allows an email to be sent from one email address to another is all about servers. In order to get from Point A to Point B, an email message is routed from server to server until it reaches the target recipient’s email server. Before we talk about how exactly this works, let’s talk about the two main categories of mail servers: outgoing mail servers and incoming mail servers.

Outgoing Mail Servers

Outgoing mail servers are also known as “SMTP” servers, which stands for Simple Mail Transfer Protocol. One of the most well-known SMTP server companies is SendGrid.

SendGrid, with its cloud-based, in-house email infrastructure, allows customers to easily send transactional emails to their recipients such as invoices, receipts, reminders and notifications without having to maintain their own SMTP server.

Incoming Mail Servers

Incoming mail servers are broken down into two main types: “POP3” which stands for Post Office Protocol Version 3, and “IMAP” which stands for Internet Message Access Protocol.

POP3 servers store sent and received email messages on a computer’s local hard drive (although most POP3 servers can also store messages on servers, too). On the other hand, IMAP servers always store copies of email messages on servers.

How an Email Travels from Point A to Point B

When you understand the essential roles of mail servers, you can more clearly visualize how they play a key part in the process of getting a message from one inbox to another. Let’s break it down into 5 essential parts:

1) Your email client connects to your domain’s smpt server

An email client, or a Mail User Agent (MUA), is a central interface that lives on a user’s desktop that allows someone to send, receive, read and write emails in one place. A web-based email client like Gmail requires users to log in to access their email accounts.

Let’s say you have a Gmail account. When you write an email and hit send, your email client (in this case, Gmail) has to connect to whatever SMTP server is associated with your domain.

2) Your email client communicates with your domain’s smpt server

Once connected, your email client (Gmail) communicates with the SMTP server. Gmail gives the SMTP server key information such as your email address, your intended recipient’s email address, and the contents of the email (including any attachments).

Then, the SMTP server processes your intended recipient’s email address. This next part might sound convoluted, but it’s actually straightforward. If your recipient’s domain name is the same as yours, the message is routed directly over to the domain’s POP3 or IMAP server.

Think of it this way: if one employee sends an email to another employee using their email addresses that have the same company domain name, the message travels straight to the domain’s server. Routing between servers isn’t necessary in that case.

However, if I send one of those employees an email from my personal Gmail account, the message does need to be routed between different servers. If the email address domains are different, the SMTP server must communicate with the other domain’s server.

3) Your smpt server communicates with the dns to find your desired recipient’s server

Next, your SMTP server communicates with the DNS (Domain Name Server) to translate the prospective recipient’s email domain name into an IP address (Internet Protocol address).

An IP address is a number that every computer connected to the Internet is uniquely assigned. As the email sender, your SMTP server can’t route an email with just a domain name. Knowing the IP address is necessary for your outgoing mail server to efficiently get the job done.

4) Your email message is routed along a series of unrelated smpt servers until it arrives at its destination

Once your SMTP server knows your recipient’s correct IP address, it can connect to the appropriate SMTP server. However, this isn’t done directly. Typically, your message is routed along a series of unrelated SMTP servers until it arrives at its destination.

5) Your email message gets the final scan of approval

Your intended recipient’s SMTP server has to scan the incoming message to determine whether or not it makes it to the inbox. If your recipient’s SMTP server recognizes the domain and the user name, it forwards the message along to the corresponding domain’s POP3 or IMAP server.

At this point, the message is placed in a “sendmail” mail queue until the recipient’s email client allows it to be downloaded. A mail queue is basically a directory that stores data and controls files for mail messages. The sendmail command is what allows the message to be delivered. Finally, your email message can be read by your intended recipient.

To Wrap It Up…

Even experienced email marketers misunderstand how servers interact to deliver emails. The next time you hit “send”, hopefully you’ll take a moment to remember how many steps are involved to get your email delivered. We hope this blog post makes you more aware of the “behind the scenes” processes that make it possible to send emails. 

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