What is Email Infrastructure?

Email or electronic mail has revolutionized the art of communication. People want a rapid and easy communication method today. Advanced technology goes into making this quick and easy way of communication between two parties possible using digital devices.

Technology Powering Sending and Receiving Emails

The following diagram illustrates the technology behind how emails are sent and received.

To send or receive an email, one needs a web browser or an email client known as the MUA – Mail User Agent. This email client (either standalone or web browser-based) reads the mail message and converts it into the machine-readable email plain text format. Email plain text is a long string of data consisting of the timestamp, recipient’s data, sender’s data, subject, and message body.

The email client then sends this text format to another program known as the MTA – Mail Transfer Agent or the sender’s server. The sender’s server uses a protocol called SMTP or Simple Mail Transfer Protocol. This server decodes the email message to determine which server the mail needs to be redirected to, for the recipient to receive the email. To do this, the MTA needs to know the IP address of the recipient’s server from the DNS address.

DNS – Domain Name Service is a program running on the server and usually listening on port 53. This service provides various information about the domain name such as MX (mail exchanger) record that contains the servers that must send and receive email. The MX record also contains the priority. Servers are tried in order of their priority. The MTA requests the MX records of the recipient’s domain from DNS.

Based on the MX record, the message is delivered to the recipient’s MDA – Mail Delivery Agent. The recipient’s MUA then downloads and converts the email from its plain text format to readable format and displays it to the user.

Email messaging is possible because the servers have a common language or a protocol for communication known as SMTP – Simple Mail Transfer Protocol. SMTP provides a common set of guidelines for the transfer of messages from one email host to another.

The SMTP process gets more complicated when thousands of emails need to be sent at one go, like in the case of marketing or transactional emails. This is when an SMTP relay comes into play.

At the receiver’s end, there is a different protocol at work, which is called POP (POST OFFICE PROTOCOL) / IMAP(INTERNET MESSAGE ACCESS PROTOCOL). SMTP protocol works well for both sending as well as receiving messages. However, when it comes to queuing incoming messages, SMTP is not an appropriate choice. Therefore, SMTP is usually paired with POP/IMAP for fetching mail messages.

POP and IMAP are two different protocols. POP is older than IMAP and assumes that the email is accessed from a single application. There is no copy left on the server in the case of POP. IMAP, on the other hand, allows simultaneous access by multiple clients.

Email Infrastructure

For a successful email marketing business, the key is to set up seamless email infrastructure to facilitate uninterrupted delivery of newsletters or bulk/transactional emails. Infrastructure includes IP addresses, mail agents, email reputation management tools, and feedback loops.

IP addresses – could be dedicated or shared. With a dedicated IP, there is no fear of a bad reputation score as it is dedicated to a single website. For a shared IP, the rating is based on the reputation of all the shared users. The risk of getting a bad rating and thus a risk of getting your email undelivered is high when using a shared IP.

Mail agents – includes Mail user agent (MUA), Mail transfer agent (MTA), and Mail delivery agent (MDA). These are the critical building blocks of your email infrastructure to successfully send or receive emails.

SMTP server – is the most vital part of your infrastructure that helps in processing your emails from your MTA to your recipient’s MDA. It plays an important role in validating email addresses, verifying email reputation, and checking the use of anti-spam filters by the recipient before delivering the email.

Feedback loops – are tools used to get an overview of your customer’s response to your email. This helps improve your campaign by providing content that is relevant and interesting to the customer.

Email reputation management tools – consists of intelligent tools that help marketers build trust with the customer. These tools help ensure that your emails are delivered successfully to the customer, without being blacklisted as spam.

So, to set up email infrastructure correctly, developers need to make sure each and every element is well-configured.


A robust email infrastructure helps you to run your business successfully, achieve your targets, and increase your market value seamlessly.

If you have any questions, please ask below!