SMTP connection should be used when Software URL and From email don’t use the same domain name.

Example: If software URL is app.yourdomain.com/admin and your email address ends with @gmail.com.

This connection type require a setup of following details: Host, Port, Username, Password, Security (Encryption type). This details can be found in your hosting / server / mailbox account. If you don’t know where to find it, please contact your hosting / server provider and ask for it.

Example:
Host: mail.example.com
Port: (25, 465, 587)
Username: [email protected]
Password: ***
Security: (SSL, TLS)

Before making the connection ensure mailbox exists on your server and for SMTP connection ensure firewall is not blocking sending emails. You can do that by login into you server (hosting) account or contact your server (hosting) provider.