To change a default Outlook form

You need to do two things to get all items in a folder to use a new form -- make the new form the folder's default and apply the new form to existing items.

Beginning with Outlook 2000, you can also substitute a custom form for any of the default forms that come with Outlook.

Change Folder Default | Substitute Default Form | Convert Existing Items | Limitations | More Information

Change Folder Default

Once you've published the form, right-click on the Contact folder or its Outlook Bar icon. Choose Properties. Then, select your form from the When posting to this folder list.

If you change the default form in the Contacts, Calendar, Journal or Tasks folder, the new form will be used whenever you click the New button for that type of item, even if you're not in the folder.

In Message folders, if you want a custom post form to appear when you double-click inside the folder or click the New button while you're in that folder, you must restrict the forms used in the folder. Go to the Forms page on the folder's Properties, and choose Only forms listed above.

Also see:

OL2000: How to Set Any Form as Default for a Folder

Substitute Default Form
(Outlook 2000)

In Outlook 97 and Outlook 98, you cannot change the default form in the Inbox folder. However, Outlook 2000 and 2002 allow a method for changing the default message form, using Windows registry entries.

Outlook 2000 Forms Administrator

Substitute your custom forms for Outlook's default forms. Download FormsAdmin.exe. This tool installs in the folder you specify during setup, along with a FormsAdminReadme.rtf file that explains how to use it. Use this tool with caution. Make sure that your substitute form includes all the functionality you need and that you enter the correct form name. The tool does not check to make sure that the form name you enter is a valid, published form of the correct type.

Also, note that the registry entries have two separate effects on new and existing items:

Existing items will open in the form whose message class you specified in the tool, but the MessageClass property on the items will remain that of the default form.
The MessageClass of new items created with the New button will be that of the custom form that was substituted. If you later remove the substitution registry entry, the MessageClass does not change. If you want the items to revert to the built-in default form, you will need to use one of the Convert Existing Items methods.

In Outlook 2002, this tool puts the registry change in the wrong key. However, you can export the .reg file and adapt it to work for Outlook 2002 simply by changing the key from
HKCU\Software\Microsoft\Office\9.0\Outlook\Custom Forms to HKCU\Software\Microsoft\Office\10.0\Outlook\Custom Forms.
Once you make that change, run the .reg file. Also see OL2002 How to Change the Default Outlook Forms.

We have had a report of forms substitution not working on message forms in Outlook 2002 SP2.

Convert Existing Items

DocMessageClass	Free tool to update the message class of existing items in any folder. Should work in any Outlook version.
Helen Feddema's VB Script method	Open and publish the ResetMessageClass.oft file, then run the published form. Older version of same script available at Update Message Class Form.
Outlook 2000 Existing Items Converter	Free Microsoft tool to change the MessageClass of existing items from the default form to a new custom form or from a custom form back to the default (e.g. IPM.Contact for contact items). This tool is a COM addin that installs in the Program Files\Microsoft Office\Office\Addins folder, along with a ChangeFmReadme.rtf file that explains how to use it. The download (Changeforms.exe) runs only for Outlook 2000. For later versions, Outlook MVP Diane Poremsky suggests using WinZip to extract the .msi file from the download and then running the .msi file to perform the installation.
Word 2000 Document to Change Outlook Folder Message Class	Self-explanatory Word 97 document that should work in all versions, as long as macros are enabled. Sample code is useful to see how to work with all items in a folder. Includes routine to analyze a folder for existing message classes.

Also see:

OL2002: How to Update Existing Items to Use a New Custom Form

Limitations

You can't import into or export from custom fields or custom forms. For workarounds, see

More Information

Outlook 2000: Release to Web Utilities -- More information on the Outlook 2000 Forms Administrator and Existing Items Converter. Download the PowerPoint presentation (2.8mb), then follow along in the Support WebCast transcript.
Microsoft Outlook 97 Administrator's Guide -- Updating Existing Items to Use a New Custom Form in Chapter 6