When sending email such as when using outlook, you must send email through your ISP (not your domain name).
For this, outgoing mail server needs to be set to the settings you receive from your ISP.
When you are sending email, almost all ISPs have now blocked port 25 and 27 – which means you cannot send email using a 3rd party server (such as your website) when you are using their internet connection.
In other words you can receive email from your server, but you must use your ISP’s servers to send email. For this they need to give you the outgoing SMTP server, username and password.
Alternatively, you can use “Forwarders” under “Mail” in cpanel to forward email@[yourdomain.com] to an email address you already use. This is an easier option.
Please call your ISP and request them to walk you through how to send out email.
This article will help you configure outlook.
For more information about email configuration, please follow this link.