unable to send emails - reason 553

unable to send emails - reason 553

Hi 

i am unable to send or receive emails from my account ( naju@pinnacleadvt.com)

it displays invalid domain . 

can you please help us out thank you.

NOte : i purchased this domain from Go daddy and i am using this email for more than 2 year s in zoho .after march 2019 i tried to use today and it shows invalid domain .

Best regards
Najumudin
najumunaju@gmail.com