Despite configuring the Outlook Junk mail filter to block emails from certain senders (by adding the addresses to the block list) emails continue to arrive in the Inbox and are not quarantined or deleted. This applies when the Default store client option has been chosen.
This is a limitation of Microsoft Outlook. Outlook does not support third party MAPI providers. Refer to the following Microsoft Knowledgebase article for more information.
This applies equally to Microsoft Outlook 2003 and 2007.
Note: Softalk Share Server clients configured in the Public Folders Only mode can perform Junk E-mail filtering as normal.