Mail Server does not accept email from NULL senders?

Hello folks, I recently setup a Cpanel/WHM VPS with a hosting provider. After the setup, I ran a DNS/email check using network-tools.webwiz.net/dns-report.htm. The report shows two errors which is of concern to me, they are: 1. Connect to Mail Server A error occured connecting to your Mail Server . 2. Acceptance of NULL Sender to . Your Mail Server does not accept email from NULL '<>' senders. Wondering what is the cause of these errors? Please not that I am able to send and receive emails from the server. Thanks for help.