What is an SMTP Server? Warren Duff July 16, 2014 Best Practices // SUMMARIES ?> Just like our SMTP Service Crash Course, we’re revisiting one of the basic elements of email deliverability: the SMTP Server. Again, we teamed up with our own Nigel Dunetts, a SendGrid Support expert, to answer a few of the most common SMTP server questions. What is an SMTP server? Simply put, an SMTP server is a machine, or collection of machines, whose primary purpose is to send, receive, and/or relay messages 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, generally formatted as smtp.serveraddress.com. Is an SMTP Server the same as a normal server? Technically speaking, yes. An SMTP server is just a server with a more specific purpose. I would recommend checking out this How Stuff Works article for a more in-depth explanation. What does the SMTP server do when I send email? Your mail client connects to the SendGrid SMTP server, smtp.sendgrid.net, using port 25 (by default). 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. 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. 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 valid DKIM and SPF signatures, and as long as there are no issues, then the recipient’s mail server will deliver the message to its intended recipient. Does SendGrid have a test SMTP server? SendGrid offers free accounts that don’t even require a credit card to enable. With a SendGrid free account, we give you access to the SendGrid SMTP server and allow you to send up to 200 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. What is the SendGrid SMTP server address? For SendGrid, the SMTP server address is smtp.sendgrid.net. Do I need to set up the SendGrid SMTP server before sending email? Nope! You just need to have an active 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. As always, you can contact us to learn more about the SendGrid email account options we provide. If you’ve already signed up for an account, but would like assistance, contact SendGrid support today!