How to: Remove Custom Form Definition Saved With a Message

How to: Remove Custom Form Definition Saved With a Message

This topic shows a code sample in C++ that converts a message that has been saved with a custom form definition to a regular message without the form definition.

In Outlook, you can share forms containing custom form pages by either publishing them to a forms library or saving the corresponding form definition with a message. A custom form saved with a message is commonly referred as a "one-off form", since the form is shared only for viewing that specific message as a one-off instance. You typically do this when the form is not published in a forms library but you want the recipient to use the custom form when opening the item. You can specify a form is a one-off in the Forms Designer, by selecting the Send form definition with item check box on the Properties page of the form.

Forms containing form pages can be customized with code in Visual Basic Scripting Edition (VBScript). Messages that are saved with form definitions are generally bigger in size. For security and storage reasons, Microsoft Office Outlook 2007 ignores form definitions saved with any item.

To convert a message that is saved with a custom form definition to one without, you must remove four named properties:

In addition, you should also remove the dispidPropDefStream property that contains the definitions of custom properties saved with that message. A side effect of removing this property is that the Outlook Object Model and the Outlook user interface will no longer be able to access user properties that have been set on the message. You are still able to access these properties and their values through MAPI. Note that if you do not remove this property and the message is saved with another form definition, dispidPropDefStream is partially overwritten with new data and data integrity is not guaranteed.

If you remove dispidPropDefStream, then you should also remove the INSP_PROPDEFINITION flag from the dispidCustomFlag property.

The following function, RemoveOneOff, accepts as input parameters a pointer to a message and an indicator whether to remove dispidPropDefStream. Using the message pointer, it calls IMAPIProp::GetIDsFromNames to obtain the appropriate property identifiers, and then calls IMAPIProp::DeleteProps to remove the named properties. It also calls IMAPIProp::GetProps to get the dispidCustomFlag property and clears the INSP_ONEOFFFLAGS flag and INSP_PROPDEFINITION flag as appropriate from that property, so that Outlook will not look for those named properties that have been removed.

  ULONG aulOneOffIDs[] = {dispidFormStorage, 
    dispidPropDefStream, // dispidPropDefStream must remain next to last in list
    dispidCustomFlag};   // dispidCustomFlag must remain last in list

#define ulNumOneOffIDs (sizeof(aulOneOffIDs)/sizeof(aulOneOffIDs[0]))

HRESULT RemoveOneOff(LPMESSAGE lpMessage, BOOL bRemovePropDef) { if (!lpMessage) return MAPI_E_INVALID_PARAMETER;

MAPINAMEID  rgnmid[ulNumOneOffIDs];
LPMAPINAMEID rgpnmid[ulNumOneOffIDs];
LPSPropTagArray lpTags = NULL;

ULONG i = 0;
for (i = 0 ; i < ulNumOneOffIDs ; i++)
    rgnmid[i].lpguid = (LPGUID)&PSETID_Common;
    rgnmid[i].ulKind = MNID_ID;
    rgnmid[i].Kind.lID = aulOneOffIDs[i];
    rgpnmid[i] = &rgnmid[i];

hRes = lpMessage->GetIDsFromNames(
if (lpTags)
    // The last prop is the flag value 
    // to be updated, don't count it
    lpTags->cValues = ulNumOneOffIDs-1;

    // If the prop def stream is not to be removed, don't count it
    if (!bRemovePropDef)
      lpTags->cValues = lpTags->cValues-1;

    hRes = lpMessage->DeleteProps(
    if (SUCCEEDED(hRes))
        SPropTagArray pTag = {0};
        ULONG cProp = 0;
        LPSPropValue lpCustomFlag = NULL;

        // Grab dispidCustomFlag, the last tag in the array
        pTag.cValues = 1;
        pTag.aulPropTag[0] = CHANGE_PROP_TYPE(

        hRes = lpMessage->GetProps(
        if (SUCCEEDED(hRes) && 
            1 == cProp && lpCustomFlag && 
            PT_LONG == PROP_TYPE(lpCustomFlag->ulPropTag))
            // Clear the INSP_ONEOFFFLAGS bits so Outlook 
            // doesn't look for the props that have been deleted
            lpCustomFlag->Value.l = 
                lpCustomFlag->Value.l & ~(INSP_ONEOFFFLAGS);
            if (bRemovePropDef)
                lpCustomFlag->Value.l = 
                    lpCustomFlag->Value.l & ~(INSP_PROPDEFINITION);
            hRes = lpMessage->SetProps(

         hRes = lpMessage->SaveChanges(KEEP_OPEN_READWRITE);

return hRes;


See Also

Constants for Outlook Named Properties