If you are using the desktop version, your version contains fully working email functions. All emails will be sent directly from your local machine. You need to configure the server setting and email delivery yourself. PTR records are important for email delivery.
For online version, the SMTP sending is limited by default to prevent spamming. The receiving is working fine directly.
In the default case, you can receive emails but can not send emails or only allowed to send a few emails per day.
This will be adjusted by system automatically according to your organization behaviours or you can contact us to upgrade your service level.