What is the Simple Mail Transfer Protocol (SMTP)? 

What is the Simple Mail Transfer Protocol (SMTP)? 

 Behind the scenes of every email sent and received is a complex system that ensures our messages reach their intended destinations. One key player in this system is the Simple Mail Transfer Protocol (SMTP), which is a set of rules that governs the transmission of emails across the internet. 

Here’s more information about SMTP and how you can set it up. 

What is the Simple Mail Transfer Protocol? 

SMTP is a protocol used for sending email messages from one server to another.  

Just as standardized addressing on envelopes facilitates postal services, SMTP standardizes email transmission from sender to receiver, enabling widespread email delivery. 

What is an SMTP server? 

An SMTP server, also called an outgoing mail server, is a computer program that sends emails using the Simple Mail Transfer Protocol. It’s a part of the mail server that specifically deals with sending and passing along outgoing emails to where they need to go. While the mail server manages both incoming and outgoing emails, the SMTP server focuses only on the outgoing ones.  

How does the simple mail transfer protocol work? 

1. Sending an Email:

When you send an email, your email client (like Outlook or Gmail) connects to your email server using SMTP. 

2. Routing the Email:

The SMTP server takes the email and routes it to the recipient’s email server. It does this by looking up the domain name of the recipient’s email address (the part after the @ symbol) and finding out which server is responsible for handling emails for that domain. 

3. Delivering the Email:

Once the email reaches the recipient’s email server, it is stored there until the recipient checks their email. 

4. Retrieving the Email:

To read the email, the recipient uses a different protocol (like POP3 or IMAP) to download the email from their server to their email client. 

SMTP is only responsible for sending emails. It doesn’t handle receiving or storing emails. That’s why other protocols like POP3 and IMAP are used in conjunction with SMTP to handle the full process of sending, receiving, and managing emails. 

How to set up an SMTP server?  

The standard procedure for SMTP configuration in a mail client involves four main steps. Here’s a breakdown of each step: 

1. Access Account Settings

In your email client, go to the “Tools” menu (or a similar section) and select “Account Settings.” This is where you can manage the settings for your email accounts. 

2. Choose the Outgoing Server Option

Look for the “Outgoing server (SMTP)” option within the Account Settings. This is where you’ll configure the settings for sending emails. 

3. Add a New SMTP Server

Click on the “Add…” button to create a new SMTP server configuration. A popup window will appear where you can enter the details of your SMTP server. 

4. Fill in the SMTP Server Details

Description: Give your SMTP server a name that you’ll recognize. It’s often helpful to use the name of your email provider (e.g., Gmail, Yahoo). 

Server Name: Enter the address of your SMTP server. You can usually find this information on your email provider’s website or by searching for “[Your email provider] SMTP server settings” online. 

Port: SMTP typically uses port 25, but it can also operate on port 587. Port 587 is often used with STARTTLS for added security. 

Connection Security: By default, SMTP doesn’t encrypt your emails. To secure your connection, you might want to use STARTTLS or SSL/TLS, which use separate ports for encrypted communication. 

  • Authentication Method: Choose the method your server uses to authenticate your identity. Common methods include password authentication, CRAM-MD5, and KERBEROS. 
  • User Name: Enter your full email address. This is often used as the username for authentication purposes. 

After filling in these details, save your settings. You may need to test your configuration by sending a test email to ensure that everything is working correctly. If you encounter any issues, double-check your settings or consult your email provider’s support resources for further assistance. 

For BigRock’s web server, you don’t need to set up a separate SMTP email server for sending emails through your website. Web servers provided by BigRock come with an SMTP server installed and are capable of sending emails. 

What are the Components of SMTP? 

The components of SMTP are: 

1. Mail User Agent (MUA):

The email client used by the sender, such as Outlook or Gmail, which allows composing and sending emails. 

2. Mail Submission Agent (MSA):

A server that receives emails from the MUA and forwards them to the Mail Transfer Agent (MTA). It ensures that the email is properly formatted and authenticated. 

3. Mail Transfer Agent (MTA):

A server responsible for transferring emails from the sender’s MSA to the recipient’s MDA. It routes emails through the internet. 

4. Mail Delivery Agent (MDA):

The final server that delivers the email to the recipient’s mailbox, making it accessible through their MUA. 

What are SMTP commands? 

MTP commands are text-based commands used to communicate between SMTP clients and servers for email transmission. Some common SMTP commands include: 


These commands are used to initiate a session between an email client and server. “HELO” is the older version, while “EHLO” is used for Extended SMTP (ESMTP) and allows for additional features. 


This command specifies the email address of the sender. It’s the first step in setting up the email envelope. 


This command specifies the recipient’s email address. Multiple “RCPT TO” commands can be used for multiple recipients. 

4. DATA:

After the “MAIL FROM” and “RCPT TO” commands, “DATA” indicates the start of the email body. The message content follows this command, ending with a single period on a line by itself. 

5. QUIT:

This command is used to end the SMTP session, indicating that the conversation is complete, and the server can close the connection. 

What are the advantages and disadvantages of SMTP? 

The Simple Mail Transfer Protocol has several advantages and disadvantages: 

Advantages of SMTP: 

  • Users can opt for a dedicated server if needed. 
  • SMTP supports sending emails in bulk. 
  • It offers a low-cost solution with a wide reach. 
  • Provides options for tracking email delivery. 
  • Ensures reliable and timely delivery of emails. 

Disadvantages of SMTP: 

  • Common SMTP ports can be blocked by firewalls. 
  • SMTP has significant security vulnerabilities. 
  • Its simplicity can limit its usefulness. 
  • Only supports 7-bit ASCII characters. 
  • Messages exceeding a certain length may be rejected. 
  • Additional processing between servers can delay delivery and increase the chance of non-delivery​ 

Where can I find SMTP servers?  

You can find SMTP servers from your email service provider or by setting up your own server. Providers like Gmail, Yahoo, and Outlook.com offer SMTP server details in their documentation or support pages. Alternatively, you can search online for SMTP server providers or consult with your email service for more information. 

What are the SMTP protocol? 

The SMTP protocol primarily uses two methods for transmitting emails: the end-to-end method and the store-and-forward method. 

1. End-to-End Method: 

In the end-to-end method of SMTP, the email is sent directly from the sender’s email client to the recipient’s email server without passing through any intermediate servers. This method is efficient in scenarios where there is a direct and stable connection between the sender and the recipient’s servers, leading to quicker email delivery. 

2. Store-and-Forward Method: 

This method is helpful when a direct connection between the sender and the recipient’s mail server is not available or reliable. The intermediate servers hold the email until a connection to the next server in the path is established, ensuring that the email eventually reaches its destination, even if there are delays or issues in the network. 

How to set up cloud-based SMTP?  

Setting up a cloud-based SMTP service typically involves the following steps: 

1. Choose an Email Service Provider:

Select a cloud-based email service provider that offers SMTP services. BigRock offers various cloud hosting plans that come with SMTP functionality.  

2. Sign Up for an Account:

Create an account with your chosen email service provider. You may need to provide payment information, depending on the provider’s pricing structure. 

3. Verify Your Domain:

Most email service providers require you to verify ownership of your domain. This process typically involves adding DNS records to your domain’s DNS settings. 

4. Obtain SMTP Credentials:

Once your domain is verified, your email service provider will give you SMTP credentials, which include an SMTP server address, port number, username, and password. 

5. Configure Your Email Client or Application:

Use the SMTP credentials to configure your email client or application’s SMTP settings. This will enable you to send emails using the cloud-based SMTP service. 

6. Test Your Setup:

Send a test email to ensure that your SMTP configuration is working correctly. Check your email client or application’s sent folder and the recipient’s inbox to confirm successful delivery. 

7. Monitor and Adjust:

Keep an eye on your email delivery metrics and adjust your SMTP settings as needed to optimize performance and deliverability. 

We hope now you have more clarity on what SMTP is. Understanding SMTP and its associated components like the SMTP server, SMTP relay, and SMTP commands is crucial for effectively managing and troubleshooting email delivery.  

Whether you’re setting up a cloud-based SMTP email service with providers like BigRock or configuring your email client, this knowledge will help you ensure reliable and efficient email communication. 


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