SMTP vs. API - Which is the best fit for your email needs?

When you own a business, usually the first point of contact your customer has are your transactional emails. This could be in the form of welcome emails, sign-up confirmations, or security codes. Transactional emails are personalized emails you send based on customer activity. They’re automated to reach your customers when a particular action is performed and it’s essential for these emails to reach on time.

Transactional emails—or any type of email, be it marketing or business emails—largely use two methods for email sending, SMTP and email APIs. As a business owner sending out emails to their customers, you’ll encounter both of these methods at some point, even if you have an admin team handling them for you. It helps to know about these methods to understand their purpose better and choose the right one. Let’s look at what these methods are and how they can be used for your business needs.

SMTP

The simple mail transfer protocol (SMTP) outlines the rules for sending emails between users. The SMTP method involves the transfer of email from one server to another and, ultimately, to the recipient using the commands defined by SMTP. It’s fairly simple and straightforward, making it easier for beginners to set up and run. Here’s how the SMTP method works:

1. The email client contacts the sending server to establish a connection. Once a connection has been established, the client transfers the sender's details to the server. This includes the email header, which includes the recipient’s details, and the subject, the email body, and additional parameters.
2. The sending server will then look for the server corresponding to the receiver and transfers this email to it.
3. Once the receiving server processes and verifies the information, the email will be available at the receiving server to be fetched by the email provider.
4. The whole process of email transfer uses SMTP to move the message across one server to the next.
5. If a user wants to use SMTP, they simply have to enter the credentials unique to their SMTP server, the TLS/SSL configuration, and their port details in their application or email client from which they will be sending out the emails.

Now that you have an idea about how SMTP works, let’s take a look at the advantages of using this method.

• One of the biggest advantages of using SMTP lies in the simplicity of its setup. You just need to enter the credentials and the port for mail transfer and you’re ready to start sending your emails.
• Another point which adds to the simplicity of usage lies in the fact that SMTP doesn't require any programming from your side, so it’s much easier to set up.
• Because SMTP is a protocol that is used universally, there won’t be any compatibility issues; it can be used with any system.

However, there are some issues you might face while using the SMTP method:

• Some servers don’t support all versions of SMTP. Older servers may not be configured to support TLS-encrypted SMTP service at certain ports as a precautionary method. As a result, those networks may deny access to some ports.
• SMTP involves back-and-forth handshakes which may slow down the system especially when sending bulk messages.

API

The application programming interface (API) acts as an intermediary between two applications performing the task it was programmed to do. This allows us to integrate one application with another using APIs to utilize its features.

Email APIs help applications access the email-sending functionality of email service providers. This is a fool-proof method that helps you , integrate your application with an email service provider (ESP) to send out your emails. Here’s a brief explanation of how APIs work:

1. Say you own an application that uses a service like ZeptoMail to send out transactional emails to your clients.
2. When an action—for example, a purchase of a product or service—occurs, an API call will be sent from your application to the ESP, prompting it to send emails to the client about the purchase on your behalf.
3. The customer's details and a security code indicating that you’re eligible to ask the ESP to send emails on your behalf will be sent.
4. The ESP will then verify the code and the email will be constructed and sent to the customer.

This is a high-level explanation of how API works. Here are some of the pros of using APIs to send your emails:

• Although APIs involve a bit of coding, they’re robust and flexible. You can include extra functionalities to support your email sending. APIs use the HTTPS protocol, which can be used to connect with the services. This doesn't require the adoption of additional software, making the operation easier.
• The delivery speed of APIs is greater than SMTP because the number of back-and-forth calls is lower. Although the margin is in seconds, this will benefit emails being sent in bulk.
• Some API providers display real-time error reports of your how your emails perform. So, even if you send an email to an email address that’s been removed from your recipient list (for bounces or other reasons), an error message will be displayed immediately. This real-time response will not be available while using SMTP.

There are some issues that you might face while using APIs, including:

• APIs require coding knowledge, and writing a set of code to do a particular task can be time-consuming.
• APIs undergo version updates and modifications, so you might have to constantly update them to suit your needs.

SMTP vs. API

So, which one is better? Some might prefer API owing to its robustness and the ability to customize to fit specific needs. Others might prefer SMTP because of its simple and easy setup.

If you’re not tech-savvy, and you’re looking for a simple method to send your emails, you can opt for SMTP. This gives you the very basic metrics of the emails you send.

If you’re interested in tinkering with code and wouldn’t mind customizing it to meet your needs, you could opt for an API. APIs give you an in-depth analysis of the emails you send, so you have all-around information to use to change your application's operations.

To make it easier to compare, here’s a table comparing SMTP and API. 
 

Both SMTP and API are reliable methods. The choice completely depends on your needs. Identifying your needs and using the right type of delivery service will help you reap their benefits.