Sendmail connection works best if Software URL and From email use the same domain name.

Example: If software URL is app.yourdomain.com/admin, your email address have to end with @yourdomain.com.

Sendmail path: This is optional setting and it should be only used if you understand how it will impact the connection, otherwise it should be left empty (software will automatically find the path).

Before making the connection ensure the mailbox exists on your server. You can do that by login into you server (hosting) account or contact your server (hosting) provider.