SMTP servers are complicated, and if you’re just dipping your toe into the how-email-gets-sent world, it’s easy to feel overwhelmed. To help you navigate your email sending—specifically, an SMTP server to send email—we’ve put together a list of the most common SMTP server questions we receive, so you’ll be an SMTP expert in no time. 

What is an SMTP server?

What does SMTP mean? We’re glad you asked. SMTP stands for Simple Mail Transfer Protocol, and it’s an application used by mail servers to send, receive, and/or relay outgoing mail between email senders and receivers. 

An SMTP email server will have an address (or addresses) that can be set by the mail client or application that you are using and is generally formatted as smtp.serveraddress.com. For example, the SMTP server Gmail uses is smtp.gmail.com, and Twilio SendGrid’s is smtp.sendgrid.com. You can generally find your SMTP email server address in the account or settings section of your mail client.

When you send an email, with SMTP host Gmail or AOL, the SMTP server processes your email, decides which server to send the message to, and relays the message to that server. The recipient’s inbox service provider, such as Gmail or AOL, then downloads the message and places it in the recipient’s inbox.

You can find more details on SMTP servers on our docs page.

Is an SMTP server the same as a normal server?

Technically, yes. Like most servers, the SMTP server processes data to send to another server, but it has the very specific purpose of processing data related to the sending, receiving, and relaying of email. An SMTP server is also not necessarily on a machine. It is an application that is constantly running in anticipation of sending new mail.

Why are SMTP servers important?

Without an SMTP server, your email wouldn’t make it to its destination. Once you hit “send,” your email transforms into a string of code that is then sent to the SMTP server. The SMTP server is able to process that code and pass on the message. If the SMTP server wasn’t there to process the message, it would be lost in translation. 

Additionally, the SMTP server verifies that the outgoing email is from an active account, acting as the first safeguard in protecting your inbox from illegitimate email. It also will send the email back to the SMTP sender if it can’t be delivered. This informs the sender that they have the wrong email address or that their email is being blocked by the receiving server.

If you’re looking for more information on SMTP, check out our post, SMTP Service Crash Course.

Common SMTP server providers & settings

SMTP Provider URL SMTP Settings
AOL aol.com smtp.aol.com
AT&T att.net smtp.mail.att.net
Comcast comcast.net smtp.comcast.net
iCloud icloud.com/mail smtp.mail.me.com
Gmail gmail.com smtp.gmail.com
Outlook outlook.com smtp-mail.outlook.com
Yahoo mail.yahoo.com smtp.mail.yahoo.com

How the Twilio SendGrid SMTP server works

What does the SMTP server do when I send email with Twilio SendGrid?

  1. Your mail client connects to the Twilio SendGrid SMTP server, smtp.sendgrid.net, using port 25 (by default).
  2. Your mail client has a conversation with our server, first verifying that the username and password used for authentication correspond to an active account, then relaying the message information, such as sender address, recipient, and message content.
  3. Our server takes the message information we gathered from your request and then repeats the conversation process in Step 2 with the recipient’s mail server.
  4. The recipient’s mail server checks the sending address, recipient address (to ensure they are a valid recipient), and message content. It checks the sending domain for any potential DNS issues, such as invalid DKIM and SPF signatures. As long as there are no issues, the recipient’s mail server will use the protocols POP3 or IMAP to retrieve the email and deliver the message to its intended recipient.

Take a look at the diagram below for a visual of the SMTP email delivery process.

Does Twilio SendGrid have a test SMTP server?

Twilio SendGrid offers free accounts that don’t even require a credit card to enable. With a Twilio SendGrid free account, we give you access to the Twilio SendGrid SMTP server and allow you to send up to 100 emails/day—this effectively gives you an SMTP server for testing. 

Active free account customers can use their account to send test messages and test their email deliverability before upgrading and sending larger amounts of email.

Do I need to set up the Twilio SendGrid SMTP server before sending email?

Nope! You just need to have an active Twilio SendGrid account and the ability to use basic username and password authentication within your email client or application.

What SMTP server port do I need to connect to?

We support unencrypted and TLS encryption on ports 25, 587, and 2525. If you’d like to implement SSL encryption, then use port 465. 

Send an SMTP email with Twilio SendGrid

Ready to get sending? Check out our documentation to learn how to send an SMTP email with Twilio SendGrid. We’ll walk you step-by-step through getting started, and we’ll also link out to other resources you might want to take a peek at.

Sign up for a free account to get started. If you already have an account but would like assistance, contact Twilio SendGrid support today!

 



Warren is the Sr. Content Marketing Manager at SendGrid, specializing in email and content best practices, he develops many of the new guides you see SendGrid release as well as other pieces of content, including blogs, videos, case studies, and emails.