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Apr, 25
What is an SMTP relay and why do we use it?
Emailing is hard. It might look easy at first – just write something smart, press ‘Send’ and wait, right? But mastering the channel’s ins and outs is not that simple. The world of email is full of complicated words like email deliverability or relay servers, confusing acronyms such as 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 take a closer look at SMTP relays. SMTP stands for Simple Mail Transfer Protocol and is the backend system that helps you and your company send, receive, and relay messages between email senders and receivers. Let’s look at what an SMTP relay 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 SMTP server (commonly referred to as a “smart host”) to another. It was first created in 1982 and continues to be the internet standard widely used today. An SMTP relay is an email relay service that works in two steps: Simple enough, right? To make things even clearer it might help to define some of the commons terms you’re likely to hear around SMTP relays: SMTP terminology Definition SMTP SMTP, or Simple Mail Transfer Protocol, is the language email servers use to send and receive messages. Think of it as the postal system for the digital world, ensuring smooth delivery of your electronic letters. Open relay An open relay is a mail server that allows anyone on the internet to send email through it, regardless of whether they are authorized users or not. This was once a common configuration, but it is now considered a security risk as it can be easily exploited by spammers and malware distributors. SMTP server An SMTP server acts like the post office for email, sending your messages to their destinations on the internet. Think of it as the digital mail truck that picks up your email and delivers it to the recipient’s mailbox. SMTP relay service With an SMTP relay service, you’re tapping into a specialized service provider that handles all the heavy lifting for you. They’ve got the infrastructure, the expertise, and the experience to ensure your emails reach their destination reliably and securely. It’s like having a team of professional mail carriers at your beck and call. Smart host Smart host and SMTP relay are used interchangeably. However, the primary difference is security: smart hosts require SMTP authentication (SMTP-auth) to relay emails, whereas SMTP relay does not. How does the SMTP relay protocol work? To better understand how an SMTP relay works, let’s imagine the journey that your normal snail mail may take to get to its destination: 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 recipient’s server. But if you were to send that campaign to someone within your organization’s domain, there would be no ‘email relay,’ as your domain’s SMTP server wouldn’t need to transfer the email to a different SMTP server. Why is SMTP relay important? Despite all this talk of SMTP relays and servers, the question remains. How does the SMTP relay process impact my email marketing efforts? Well, as an email marketer, understanding the SMTP relaying process and its role in bulk emailing is important for several reasons: Widespread usage SMTP is one of the most widely adopted protocols for email transmission (along with email APIs). Many senders use it to send and receive emails. This makes SMTP crucial for ensuring your marketing emails reach their intended audience across various email providers, regardless of their location. Email campaign performance SMTP protocol allows email delivery and tracking platforms, to more accurately analyze the performance of email campaigns. Monitoring SMTP response codes can provide insights into the success of your email deliveries, including delivery rates and open and click rates, and identify potential issues that need addressing. Email bounce monitoring When an email cannot be delivered to the recipient’s inbox for various reasons (an email address doesn’t exist, the mailbox is full, etc.), the receiving server sends a bounce notification back to the sender. The SMTP protocol helps email delivery and tracking platforms manage these email bounce messages, allowing you to clean and maintain your email lists to improve deliverability and sender reputation. SMTP authentication and security SMTP authentication mechanisms, such as SMTP AUTH, enable you to add basic email authentication protocols such as SPF and DKIM. These help guard your campaigns from email spoofing, spam, and phishing attacks. Additionally, SMTP uses TLS (Transport Layer Security) – the successor to SSL (Secure Socket Layer) – to encrypt communication between email servers, further enhancing the security of your email communications. 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? 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 (email marketing campaigns and transactional emails) 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 routes it through SMTP server to prepare and send it out to recipients. To combat spam, many webmail providers and email clients (i.e., Gmail, Microsoft 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
