You really should not be using CDO 1.21 from C# or any other .NET language.
Neither CDO nor Extended MAPI is supported in .NET code at all and while it
may work most of the time things will fail, usually at a client site and no
one will be able to support you at all.
// toAdd = x-header to add to mail item.
// ID = MailItem.EntryID, item must be saved to have an ID.
// StoreID is the EntryID of the Store where the item is located. Use
item.Parent.StoreID to get it.
private void AddHeader(string toAdd, string ID, string StoreID)
// see http://support.microsoft.com/kb/195656
for how to convert
// a MAPI tag to a CDO tag
const string propSet = "8603020000000000C000000000000046";
MAPI.Session cdo = new MAPI.Session;
cdo.Logon "", "", false, false, missing, missing, missing;
MAPI.Message item = (MAPI.Message)cdo.GetMessage(ID, StoreID);
MAPI.Fields fields = (MAPI.Fields)item.Fields;
MAPI.Field header = fields.Add("MyHeader", 8, toAdd, propSet);
After that, since Outlook doesn't really know about changes made to an item
outside of its scope you should do something like this to make it aware of
Outlook.MailItem mail.Subject = mail.Subject;
[MVP - Outlook]
Author: Absolute Beginner's Guide to Microsoft Office Outlook 2003
Reminder Manager, Extended Reminders, Attachment Options
"Bharathi Harshavardhan" wrote in message
> I have a requirement where i need to store some information into the x-
> header of an outlook email.
> I am using Outlook 2003 and Visual Studio 2005(C#). I have created a
> shared Addin project.
> I got to know that x-headers cannot be created using Outlook Object
> Model. I want to use CDO 1.21 for this purpose.
> Could anyone please assist me how to add x-header to an outlook email
> using CDO1.21.
> Thanks in Advance