Click Tools > Junk Mail Handling.
Click Automatically Delete Items __ Days After Delivery (Move to Trash).
Specify how long you want items retained in the Junk Mail folder.
Click OK.
All items from e-mail addresses and Internet domains in the Junk List are delivered to the Junk Mail folder.
To manually delete items from the Junk Mail folder, right-click the Junk Mail folder > click Empty Junk Mail Folder > Yes.