Truncated Outlook email headers retrieved using VBA - vba

Question

I want to access the email headers in Outlook 2010.
I use the code below but unfortunately the result contains only the first 252 characters of the header. Any suggestion on what I'm doing wrong?
Dim strHeader As String
strHeader = GetInetHeaders(olItem)
MsgBox "Truncated string: " & strHeader
and
Function GetInetHeaders(olkMsg As Outlook.MailItem) As String
' Purpose: Returns the internet headers of a message.'
' Written: 4/28/2009'
' Author: BlueDevilFan'
' Outlook: 2007'
Const PR_TRANSPORT_MESSAGE_HEADERS = "http://schemas.microsoft.com/mapi/proptag/0x007D001E"
Dim olkPA As Outlook.PropertyAccessor
Set olkPA = olkMsg.PropertyAccessor
GetInetHeaders = olkPA.GetProperty(PR_TRANSPORT_MESSAGE_HEADERS)
Set olkPA = Nothing
End Function

Answer 1

Msgbox is not a good method of proving truncation. Text can be legitimately truncated.
Text in a mailitem does not appear to be truncated. At least I do not notice cut off information.
Private Sub Test_GetInetHeaders()
Dim olNewmail As mailItem
Dim strHeader As String
Dim olItem As mailItem
Set olItem = ActiveInspector.currentItem
strHeader = GetInetHeaders(olItem)
Set olNewmail = CreateItem(olMailItem)
olNewmail.body = strHeader
olNewmail.Display
MsgBox "Truncated string if limit exceeded: " & strHeader
ExitRoutine:
Set olItem = Nothing
Set olNewmail = Nothing
End Sub
Function GetInetHeaders(olkMsg As outlook.mailItem) As String
' Purpose: Returns the internet headers of a message.'
' Written: 4/28/2009'
' Author: BlueDevilFan'
' Outlook: 2007'
Const PR_TRANSPORT_MESSAGE_HEADERS = "http://schemas.microsoft.com/mapi/proptag/0x007D001E"
Dim olkPA As outlook.propertyAccessor
Set olkPA = olkMsg.propertyAccessor
GetInetHeaders = olkPA.GetProperty(PR_TRANSPORT_MESSAGE_HEADERS)
Set olkPA = Nothing
End Function

Answer 2

The PropertyAccessor class has some limitations. One of them is that string properties are limited in size depending on the information store type. You need to use a low-level API - Extended MAPI for reading properties without limitations introduced by the OOM. The OpenProperty method of the IMAPIProp interface returns a pointer to an interface that can be used to access a property. Here is what MSDN library states:
The IMAPIProp::OpenProperty method provides access to a property through a particular interface. OpenProperty is an alternative to the IMAPIProp::GetProps and IMAPIProp::SetProps methods. When either GetProps or SetProps fails because the property is too large or too complex, call OpenProperty.
Or you may consider using third-party wrapper around Extended MAPI (for example, Redemption).