Outlook 2003 allows the user to use a registry key to open up access to blocked attachments.
To open blocked attachments using a registry key, follow the next steps:
Note: Always make a backup before editing the registry.
1. To open the Registry Editor, go to Start -> Run, type regedit and click OK.
2. Expand HKEY_CURRENT_USER\Software\Microsoft\Office\10.0\Outlook\Security.
(For Outlook 2000 SP3, change 10.0 to 9.0 or 11.0 for Outlook 2003.)
3. Under that key, add a new string value named Level1Remove.
4. For the value of Level1Remove, enter a semicolon-delimited list of file extensions. For example, entering .mdb;.url would unblock Microsoft Access files and Internet shortcuts. Note that the use of a leading dot was not previously required; however, new security patches may require it. If you are using mdb;url format and extensions are blocked, add a dot to each extension. Note also that there is not a space between extensions.
5. The modifications you made will take effect after you restart Outlook.