1. Login to the Zimbra Webmail using respective username and password.
2. Select on the particular email that you want to mark as a spam, right click on that mail and click on “Mark as Spam”, as shown on the below figure.
3. After clicking “Mark as Spam”, selected mail will be move to the webmail junk folder.
4. To mark not as a spam, go to the junk folder and right click on particular email and click on “Mark as Not Spam”. After clicking selected mails are move to the inbox.