How can an SMTP Relay Service help your Business?

Simple Mail Transfer Protocol widely known as SMTP is a TCP/IP protocol used by professional and free SMTP Servers allowing you to seamlessly transmit emails across the web.

I guess you already knew that, but I had to start this article somehow.

Besides that, I am here to show you how to send unlimited transactional emails to your email subscribers using a free SMTP server.

If you’re contemplating which service to use, one of the best in the SMTP relay service provider in the market in terms of deliverability as well as pricing is Pepipost. 

What is an SMTP Server?

An SMTP Server can be described in layman terms;

As a piece of computing machinery that makes sure that your email gets delivered to the right email address across the world wide web. Simple enough, right?

To understand it even better you can directly correlate it to the current brick and mortar mailing system.

In that case, the SMTP Server acts as the mailman of our traditional mailing system.

How does an SMTP Relay Service Work?

When an email is sent from your computer, your email client sends your email to its destination over the SMTP protocol. The SMTP server then looks up the destination of the email and transmits the email to the server closest to/ to the destination server. This server then looks up the email domain and passes your email onto the next email server. The mail server of the recipient then stores the email and keeps it ready for the email client of the recipient to collect it. The recipient collects the email from the mail server using a mail client that uses the protocol POP3 or IMAP (or webmail using a web browser)

This can be understood better by the most common example of sending a letter when you send a letter with a correct address on it, you drop it off at your nearest post office. The post office then transfers all the letters in a hub, sorts the letters by their destination and sends it to the respective hubs. These hubs then further bifurcate the letters based on addresses until the letter reaches the letterbox of the recipient who collects it from their letterbox.

When your server knows the IP address of your recipients’ email server, it will attempt to connect to this server on the SMTP port. Port 25 for SMTP is the most commonly used port for sending emails online.

When connected, your server will say "Hello, I have an email for ''". The SMTP email server at then replies saying "OK, please start the transmission of your email". This is also an important part of transmission so that during information exchange, none of the important information is lost.

If the server isn't responsible for receiving email for, it will inform your server causing it to return the email with an error. These errors can happen when your server is using a DNS server that is not up-to-date. It is therefore very important that your server uses the correct DNS server. You should be careful and consider all the factors before choosing a DNS server.

In some cases, your email server doesn't need to do the DNS/MX lookup. These are the cases where you have a smart host your server can forward all it's outbound emails to. A smart host will then either do the DNS/MX lookups itself or forward the message to another server/host to do the DNS/MX lookup.


That concludes our article about Google’s Free SMTP Servers and Pepipost’s paid one and why you should opt in!

It is evident that as a business you will definitely need to consider a more sophisticated SMTP approach.

Pepipost is one of the few ESPs that allows you to send unlimited emails through our SMTP Server even on the lowest tier of plans!