HOW TO DELETE UNDELIVERED MAIL AND MAIL ADDRESS IN ZOHO

HOW TO DELETE UNDELIVERED MAIL AND MAIL ADDRESS IN ZOHO

I SENT MAIL UNAVAILABLE MAIL ADDRESS AND I DELETE MAIL FROM MY SENT BOX BUT STILL I CAN SEE NOTIFICATION IN MY SENT BOX AND UNAVAILABLE MAIL ID SUGGEST WHEN I CREATE A NEW MAIL.
SO HOW I CAN DELETE IT BOTH.