Emailing is hard. It might look easy at first–just write something smart, press ‘Send’ and wait, right? But mastering the ins-and-outs of emailing is actually not that simple. The world of email is full of complicated words like email deliverability or relay servers, confusing acronyms like SMTP, MTA or IMAP, and detailed metrics that need to be understood.

Setting up contact lists and creating your first newsletter are great starting points, but if you’re looking to take the next step in your understanding of email marketing, then you should probably take a closer look at SMTP relays.

SMTP stands for Simple Mail Transfer Protocol, and is essentially the backend system that helps you and your company send, receive, and relay messages between email senders and receivers. Let’s take a look at what it is and how it works.

What is an SMTP Relay?

An SMTP relay is a protocol that allows email to be transmitted through the internet, from one server to another, for delivery. It was first created in 1982 and continues to be the internet standard that is widely used today.

An SMTP relay is an email relay service that basically works in two steps:

  1. It receives the outgoing mail from the sender (that is, your amazing Groundhog Day’s email campaign).
  2. It delivers it to the recipient’s local post office, another SMTP server.

Simple, right?

Hold on, but what is ’email relay’?

OK, so maybe not that simple yet. To break this down a bit more, let’s imagine the journey that your normal snail mail may take to get to its destination:

snail mail

Email relay is the process of transmitting an email message from one server to another. In the picture above, the local post offices would be the SMTP servers and the email transfer that happens between them is what we call ‘relaying’.

So for example, when you send out your latest campaign ‘Cute Puppies Looking For A Foster Home’, your company’s SMTP server relays your email to the server owned by your recipient. But if you were to send that campaign to someone with your same domain, there would be no ‘email relay’, as your SMTP relay server wouldn’t need to transfer the email to a different SMTP server.

Sending through an SMTP server with an email service provider

So what does this protocol look like when it comes to an email service provider like Mailjet? Getting the most out of your own SMTP relay server is not easy, so most businesses that need to send mass email to their customers use SMTP relay for ease of maintenance and added analytics insights.

Sending through an email service provider via an SMTP relay saves companies from having to run their own mail server. As you can see in the diagram below, the business or sender creates the email and their server sends it to Mailjet’s SMTP server to prepare and send it out to recipients.

smtp (4)

In order to combat spam, a majority of webmail providers and email clients (i.e. Gmail, Outlook, Yahoo, etc.) put a limit on how many emails you can send to different recipients per day. As businesses, who need to communicate en mass with their audience, would often exceed this limit, they will require the services of an enterprise level email sending platform. Like Mailjet, yes. 😉

An SMTP relay provider can help businesses and organizations deliver large volumes of email without getting them mislabeled as spam or running up against small sending limits.

Email service providers invest a lot of resources into building their own email infrastructure to handle large volumes and work closely with the major internet service providers (ISPs) and webmail providers to improve email deliverability and deliver these emails straight to the recipients’ inbox.