Click on the 'Add SMTP server' button and you are directed to the form to fill these following details:

Name - A unique name to identify the email gateway configuration. Ex: "Support Email Gateway.
Description - A brief note explaining the purpose of this email gateway. Ex: "Used for sending automated ticket updates."
Server Address (Host) - The email server’s address that processes outgoing emails. Example: "smtp.example.com"
Port - The communication channel through which emails are sent. Common values: 465 (SSL), 587 (TLS), or 25.

From Email Address - The email address that will appear as the sender for outgoing emails. Ex: notifications@yourcompany.com
Username/Password - The login credentials for authenticating with the email server, ensuring secure email sending.

How to integrate Email Gateway on Grid?