What is SMTP (Simple Mail Transfer Protocol) and How does it work?

Communication is one of the core parts of any civilization from the beginning. The world is moving forward in becoming a wide digital civilization. All thanks to effective & fast communication. Emails are an effective way to communicate. It has played a very vital role in shaping how we communicate. Email is used for personal as well as corporate communication. When you focus on corporate communication, you can segregate emails for internal communication or external communication with your clients, creating a brand image, generating leads, etc. To send such a huge amount of emails, you need a Simple Mail Transfer Protocol Server or SMTP Server in place.

We all know that emails are the most efficient way to communicate. The whole system of emails has been transformed by Simple Mail Transfer Protocol Server or SMTP servers. Using SMTP Servers is analogous to using posts in the old times where you used to have a postman who used to get his posts through a head office. The whole system combined from the start (You drop your posts) to finish (where you use to receive your posts) was called the mailing system. It’s just ironic that the whole physical system has transformed and come on digital platforms now. 

What is an SMTP server? 

An SMTP server is also called a Simple Mail Transfer Protocol Server. It is essentially an application that sends, receives, and relays emails. The important task of an SMTP Server is to act as a relay for outgoing mail between an email sender and an email receiver. It’s essential to note that an SMTP Server is not a server but just an application that enables the sending and receiving of emails.

Every SMTP server has its address which is usually in smtp.serveraddress.com format. A common doubt usually arises between SMTP and IMAP/POP. But there is a very subtle difference between the two. SMTP is a push protocol used to send emails, whereas POP (post office protocol) or IMAP (internet message access protocol) is used to retrieve those emails at the receiver’s side.

SMTP stands for Simple Mail Transfer Protocol. It allows the software to transmit electronic mail over the internet. They use proper authentication, which increases the chances that your emails get delivered to users’ inboxes. There are multiple free and paid SMTP service providers. The primary function of an SMTP service provider is to handle the sending, receiving, and relaying of emails. The free SMTP inbox providers like Gmail have default SMTP servers, but you can also change them to custom ones like SendinBlue. 

Email messages transverse SMTP to relay messages from your server to the recipient’s server to be delivered and read by the end-users. You need to configure email sending settings. SMTP service providers are third-party email service providers that send emails from your site or server. You will have to choose the right service provider to manage the email sending. Some companies select to set up and monitor their SMTP server to send the emails to their subscribers. At the same time, other companies may choose reliable SMTP service providers to handle their emails for them. You can easily monitor marketing and transactional email streams using the SMTP service. 

Using an SMTP server, you can send and track transactional emails through GetResponse via SMTP or API. After you’ve purchased the add-on, you will need to use an SMTP or API integration to start sending messages through any SMTP server. Also, the add-on allows you to use GetResponse as a transactional email sending service only. It would be best to use message templates available in your eCommerce CMS or use one of your plain text or HTML messages to create messages. Also, the transactional email is a paid add-on. Its price is based on a monthly send limit. 

An SMTP Protocol or Server Mail Transfer Protocol is a set of rules for Digital Communication, i.e., Electronic mail transmission. The SMTP servers are the applications whose main function is to send, receive or Switch between outgoing mail senders and receivers. There are a bunch of free online SMTP servers through which you can send free emails. 

Types of SMTP Servers

  1. Normal SMTP Servers 
  2. SMTP Proxy Server 

Normal SMTP Servers

It is an ordinary SMTP server that acknowledges emails and lines, which the receiver gets. It necessitates that you determine many nearby domains taken care of by the server. If any email comes in from an alternate domain and a pass-on message is permitted, it will be conveyed to its destination server. SMTP servers can be used for bidirectional bound delivery services—I.e, inbound or outbound. You can easily use the SMTP server in your email marketing strategy to increase your sales.

SMTP Proxy Servers 

Proxy servers are not Fully functional like SMTP servers, but it requires an actual SMTP server to connect. Users connect to actual SMTP servers through a proxy server so that they can block unnecessary mails, monitor their emails, and even alter their content.

List of Top SMTP Service Providers 

  1. Mail Baby: Mail Baby is the most potent SMTP service provider. The service is an email smart host that offers outbound filtering. Emails are sent to MailBaby systems and are analyzed for content. Email is then routed through an email zone based on the email content and score of the email or bounced as spam.
  2. SMTP.com: SMTP.com is another most popular SMTP service provider. It is used by over 100,000 businesses worldwide. They offer a robust API to send transactional emails, seamlessly integrating with WordPress using the popular WP Mail SMTP plugin. Also, the SMTP relay is the core focus of their business. Also, the service offers one of the best deliverability with high email volumes.
  3. SendinBlue: SendinBlue is a complete SMS and email marketing software for businesses. They are one of the fastest-growing email marketing platforms. SendinBlue is an all-in-one email marketing plugin that includes various features to make email list building and management simple.
  4. Google Workspace: G Suite is Google’s productivity suite for businesses. It allows you to use the calendar, Google Drive, Docs, Photos, and Gmail with your domain name. It will enable you to get a professional business email address while still using the familiar interface of Google.
  5. MailGun: Mailgun is a popular SMTP service provider for developers and businesses. They offer powerful APIs to send transactional emails. It is easy to integrate into your WordPress website. Whether you are an eCommerce store, a membership website, or a small business, Mailgun offers an easy-to-scale SMTP service to send your marketing and transactional emails.

How to Use SMTP servers?

Now, you have an idea about SMTP and SMTP servers. The main Question arises why and when we Use SMTP servers. There are various Email Service providers available now, i.e., Gmail, Yahoo Mail, etc., which we use in our day-to-day mailing and for business purposes. But they have certain limitations that an SMTP server can resolve. SMTP servers can be used to both drip marketing emails and transactional emails.

The major purpose of using SMTP servers instead of Common Email Providers is Scaling, which is only possible with Dedicated SMTP servers. Let us first understand this with an example: You run a business, and you need to send multiple emails or bulk mails regarding promotional offers, acknowledge User activity on the website such as password change, forget the password, Sign up process, etc. To manage all these, you will need a system that can not be done by sending mail from a web interface that is not an option. 

You will need to get any SMTP service’s credentials for sending emails. Also, it allows you to use the API key for sending and tracking transactional emails. However, you will have to purchase the transactional email add-ons first. Transactional emails are paid add-ons. To get the credentials from an SMTP service provider, you will have to have a transactional email add-on. You can only use the transactional email add-on if you have a premium account. We have explained the detailed guide on how to obtain SMTP credentials below. If you are setting up transactional email by API key, you will need to generate the API key from your SMTP service account. Also, the generated API keys will be available for only 90 days. You can access their web services using the API keys. 


The SMTP (Simple Mail Transfer Protocol) service allows the software to send your users or customers from your WordPress websites. Also, there are multiple popular SMTP service providers in the market. However, most of the SMTP service providers are paid. Only a few of them provide SMTP services for free. We have mentioned the process of SMTP integration and the types of SMTP servers. Various SMTP servers provide free as well as paid services. However, many free SMTP servers in the market offer all essential features. We hope this article will help you understand the SMTP servers and their types. Also, you can understand the types of SMTP and help you choose the right SMTP servers for your store or business.

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