We accept unencrypted connections on ports 25, 587, & 2525, TLS encryption on ports 25, 587, & 2525, and SSL encryption on 465. You can test for open ports using the following telnet command, subsituting # for a port number:

>telnet smtp.sendgrid.net #

To begin, open your Windows menu, type cmd into the search function, and press enter. 

If you are using a Mac, launch the Terminal application. 

You should now be looking at a DOS-prompt style window with a blinking cursor in the top left-hand corner, you will use this window to input the commands to initiate a telnet connection. Use the progression below to walk you through the connection, every line starting with > is a command you will type and subsequently press the <enter> key afterwards.

>telnet smtp.sendgrid.net # <enter>
220 xxxx ESMTP service ready
>EHLO <enter>
250-xxxx
250-8BITMIME
250-SIZE 20480000
250-AUTH=PLAIN LOGIN
250-AUTH PLAIN LOGIN
250 STARTTLS
>auth login <enter>
334 VXNlcm5hbWU6
>your BASE64 encoded SG username <enter>
334 UGFzc3dvcmQ6
>your BASE64 encoded SG password <enter>
235 Authentication successful. ***

*** This indicates that your conection to smtp.sendgrid.net over the selected port is open, and your username and password are valid as authentication credentials.

Continued, Sending a message using Telnet.

>mail from: fromaddress@domain.com <enter>
250 Sender address accepted
>rcpt to: toaddress@domain.com <enter>
250 Recipient address accepted
>data <enter>
354 Continue

>To:To Name <enter>
>From: From Name <enter>
>Subject:Testing <enter>

> <enter> you need to enter one blank line before you start the actual body of the message

>This is the body of the message you would like to send. <enter>
>. <enter> typing a period(.) tells us you are finished, and to send the message
250 Delivery in progress

>quit <enter>
221 See you later


Connection to host lost.

Note: If upon attempting 'telnet smtp.sendgrid.net #', you receive an error stating "'telnet' is not recognized as an internal or external command, operable program or batch file." this means that Telnet is not installed on your machine. This can be done by visiting your "Add and Remove Progams" section within your Control Panel, and installing the 'Telnet Client' and 'Telnet Server' packages within 'Turn Windows features on or off".