--- title: "Everything You Need To Know About SMTP Server And Why Do You Need One | DuoCircle" description: "The Simple Mail Transfer Protocol (SMTP) server is a communication protocol or the technology behind email communication." image: "https://www.duocircle.com/images/og-default.png" canonical: "https://www.duocircle.com/blog/outbound-smtp/everything-you-need-to-know-about-smtp-server-and-why-do-you-need-one/" --- Quick Answer An SMTP (Simple Mail Transfer Protocol) server is the technology that transports email between sender and recipient. Every SMTP server has a unique address (e.g., smtp.gmail.com) configured in the mail client. When you click Send, the client connects to the SMTP server on a specified port (commonly 25 or 587), passes the sender, recipient, and body, and the server splits the recipient address into local and domain parts. If the sender and recipient are on the same domain, the server delivers locally via the inbound retrieval protocol (e.g., POP3); otherwise it looks up the recipient domain's IP, validates the sender is active, and hands the message to the recipient's SMTP server. Failed deliveries return to the sender with a status. Configuring an SMTP server in a client requires: description, server name, port (25 or 587), connection security (SSL/TLS optional), authentication method, and username. To test connectivity, run 'telnet '; status code 220 means working, no response usually means a firewall or antivirus is blocking the connection. Share [ ](https://www.linkedin.com/sharing/share-offsite/?url=undefined%2Fblog%2Foutbound-smtp%2Feverything-you-need-to-know-about-smtp-server-and-why-do-you-need-one%2F "Share on LinkedIn") [ ](https://twitter.com/intent/tweet?text=Everything%20You%20Need%20To%20Know%20About%20SMTP%20Server%20And%20Why%20Do%20You%20Need%20One&url=undefined%2Fblog%2Foutbound-smtp%2Feverything-you-need-to-know-about-smtp-server-and-why-do-you-need-one%2F "Share on X/Twitter") [ ](https://www.facebook.com/sharer/sharer.php?u=undefined%2Fblog%2Foutbound-smtp%2Feverything-you-need-to-know-about-smtp-server-and-why-do-you-need-one%2F "Share on Facebook") [ ](https://reddit.com/submit?url=undefined%2Fblog%2Foutbound-smtp%2Feverything-you-need-to-know-about-smtp-server-and-why-do-you-need-one%2F&title=Everything%20You%20Need%20To%20Know%20About%20SMTP%20Server%20And%20Why%20Do%20You%20Need%20One "Share on Reddit") [ ](mailto:?subject=Everything%20You%20Need%20To%20Know%20About%20SMTP%20Server%20And%20Why%20Do%20You%20Need%20One&body=Check out this article: undefined%2Fblog%2Foutbound-smtp%2Feverything-you-need-to-know-about-smtp-server-and-why-do-you-need-one%2F "Share via Email") ![SMTP Server](https://media.mailhop.org/duocircle/images/2020/08/email-migration-service-5054.jpg) The Simple Mail Transfer Protocol (SMTP) server is a **communication protocol** or the technology behind email communication. In other words, _SMTP is the protocol that allows you to send and receive emails_. Every SMTP server has a unique address and needs to be set up in the mail client that you are using. If you are using SMTP host Gmail for example, then the SMTP address is smtp.gmail.com. If you want to find the address of the SMTP server you are currently using, you can easily find it in your email client settings. ## Why You Need An SMTP Server? _Without an SMTP server, you cannot send your email to its destination_. When you click the “send” button from your email client, your email messages get automatically converted into a string of codes and are transferred to your SMTP server. There, the codes are processed accordingly, and the message is relayed to the correct email address. If there is no [outbound SMTP](/email/outbound-smtp) server, then the email message cannot be sent to the recipient and could even get lost in the conversion process. Along with relaying SMTP email messages, _the server also checks whether an active or working email account is sending the outgoing message_. In case the email cannot be delivered, it ensures that the email goes back to the sender. This action is to let the sender realize that he has the wrong email address or the receiving server blocks emails from the sender’s ID. [![SMTP Email Server](https://media.mailhop.org/duocircle/images/2020/08/Key-Statistics-SMTP-Email-Servers.jpg)](https://media.mailhop.org/duocircle/images/2020/08/Key-Statistics-SMTP-Email-Servers.jpg) ## How SMTP Server Works? When you send an email, this is what happens in the background in the SMTP server (let’s assume that Outlook Express is used here to send the email): - The email client (Outlook Express) connects to the SMTP server through the specified port (say 25). - The email client communicates with the SMTP server with all the details of the email message, including the sender email ID, receiver email address, and body of the email. - Now the SMTP server springs into action and breaks the recipient email address into two parts, name and domain name. For example, if the recipient name is _[john@gmail.com](mailto:john@gmail.com)_, the email address is split into _john_ and _gmail.com_. - If the sender email address also comes from _@gmail.com_, the process is quick and straightforward for the SMTP server. It uses a delivery agent program to deliver the email to that address using the POP3 server for Gmail. But if you are using a [hosted SMTP](/email/hosted-email) server, then the process takes some time. - Every domain name, like the free SMTP hosting provider, Gmail, has a unique IP address, and the SMTP server gets the IP address of the recipient. The server checks whether the sender’s email address is an active address to **prevent spam emails** and then hands over the message to the recipient SMTP server. - The recipient SMTP server then takes care of delivering the email address to the recipient’s inbox. - In case the recipient email address is incorrect, or if the recipient **SMTP relay service** rejects the email message from the sender, it returns the email to the sender with appropriate information. ## How To Configure An SMTP Server In 4 Simple Steps _Setting up an SMTP server is pretty simple_. Follow the steps as detailed below: **Step 1:** Open the [email client](https://en.wikipedia.org/wiki/Email%5Fclient#:~:text=An%20email%20client%2C%20email%20reader,and%20manage%20a%20user's%20email.) and go to Tools à Account Settings. **Step 2:** Choose “Outgoing Server (SMTP).” **Step 3:** Click the “Add” button to add a new SMTP server. **Step 4:** In the next window, provide all details including your description, server name, port address, connection security, authentication method, and username. **Description**: In the description field, give a name to identify your email server. If you are setting up your Gmail account in Outlook, then provide _Gmail_. If you are setting your company email address, then give it as _Company Mail_, and so on. **Server Name**: This is where you will provide the SMTP server name of your email account. If you are setting your [Gmail account](https://www.digitalocean.com/community/tutorials/how-to-use-google-s-smtp-server), give _smtp.gmail.com_ as the server name. _You can also buy SMTP server from email hosting providers and provide the address of that here_. **Port**: Generally, port 25 is used for sending emails. But port 587 can also be used to send emails. **Connection Security**: By default, [SMTP servers](https://www.ionos.com/digitalguide/e-mail/technical-matters/smtp-server/) don’t encrypt email messages. But if you need to **use encryption**, then you can use the SSL/TLS extension, too. **Authentication Method**: If you want to use a password, then you can choose “Password, transmitted insecurely.” **Username**: Provide the username of the email address. [![SMTP Server](https://media.mailhop.org/duocircle/images/2020/08/Office-365-migration-5053.jpg)](https://media.mailhop.org/duocircle/images/2020/08/Office-365-migration-5053.jpg) ## How To Check If Your SMTP Server Is Working? At times, even though you provide the right email address and SMTP server, the mails won’t go through. So, to _test whether your SMTP server is working or not_, you can use the following method - Open command prompt, type _telnet_ along with your SMTP address and port address like: **telnet smtp.gmail.com 25** - If the SMTP is working, then a message with the status code _220_ is returned. - If there is no response, then it means some antivirus or firewall is blocking your SMTP server from relaying your message. ![Brad Slavin](https://media.mailhop.org/dmarcreport/images/team/brad-slavin.jpg) Brad Slavin General Manager General Manager at DuoCircle. Product strategy and commercial lead across the email security portfolio. ## Secure your email infrastructure Protect, authenticate, and deliver. Contact our team to find the right solution. [Contact Sales](/contact/) [Explore Products](/products/) ## Related Articles [ SMTP 7m Office Copiers Can't Authenticate to Microsoft 365 Anymore: Why It Broke and How to Fix It May 5, 2026 ](/blog/office-copiers-cant-authenticate-to-microsoft-365-the-fix/)[ SMTP 3m A Quick Guide To 5 Free SMTP Plugins For Your Domain Nov 20, 2020 ](/blog/outbound-smtp/a-quick-guide-to-5-free-smtp-plugins-for-your-domain/)[ SMTP 5m All You Need To Know When You Buy SMTP Server For Email Marketing May 19, 2020 ](/blog/outbound-smtp/all-you-need-to-know-when-you-buy-smtp-server-for-email-marketing/)[ SMTP 8m The Blacklisted Email IP: The Digital Pariah That Can Impact Your Business Jan 6, 2018 ](/blog/outbound-smtp/blacklisted-email-ip-digital-pariah-can-impact-business/) ```json {"@context":"https://schema.org","@type":"Organization","name":"DuoCircle LLC","url":"https://www.duocircle.com","logo":{"@type":"ImageObject","url":"https://www.duocircle.com/images/duocircle-logo.png"},"description":"DuoCircle is a portfolio of specialized email products covering protection, authentication, delivery, and routing. 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