Microsoft Outlook has built-in feature to block attachments of unsafe extensions to protect users from malicious code and viruses. Unfortunately this blocking of attachment is not smart enough and often it also blocks genuine attachment with emails.
Also there is no easy way to unblock those extension and you have to mess with registry to do so. Here is an excellent tool Outlook Attachment Enabler to block and unblock extensions on Microsoft Outlook 2010, 2007, 2003 & Office Xp.
Features of Outlook Attachment Enabler
1. Control what attachments Outlook has deemed to be unsafe
2. Add to the default list of blocked attachment types.
3. Includes the full and complete list of what Outlook will block by default
Outlook Attachment Enabler for Outlook 2010
Download Outlook Attachment Enabler for Microsoft office 2010 Outlook.