1. Login to the webmail, as shown on the figure below.
Webmail URL: http://webmail.example.com
2. Now click on the Preference tab and select Mail option from the left hand side menu.
3. Now scroll down the webpage and go to the section "Access from other mail client" enable the "Include Junk Folder" checkbox, as shown on the figure below.
4. Now check by Send/Recieve mails from the Outlook to download the all mails.