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, 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?

An SMTP (Simple Mail Transfer Protocol) server is an application that’s primary purpose is to send, receive, and/or relay outgoing mail between email senders and receivers. 

An SMTP 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, Gmail’s SMTP server address is smtp.gmail.com, and Twilio SendGrid’s is smtp.sendgrid.com. You can generally find your SMTP server address in the account or settings section of your mail client.)

When you send an email, 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 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.

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.

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. 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. Here’s more information on how to send an SMTP email with Twilio SendGrid.

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

 



Warren Duff
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.