How to access a user property of a custom outlook mail item with Redemption in C#

I’m trying to write a C# application that opens up a outlook custom mail item and fill in multiple user properties. I was able to do so by using the Microsoft Outlook Interop. But I had the annoying security warning each time I tried to change some user property. I found out that Redemption is the perfect tool to avoid this. But when I try to change a user property, Redemption creates a new one instead of using the already existing one.

This is the code I used to change the property with Outlook Interop (Pops up a security warning) :

string customPropertyNamespace = "http://schemas.microsoft.com/mapi/string/{00020329-0000-0000-C000-000000000046}/";    
Outlook._Items oItems = oPublicFolder.Folders["Babillards"].Folders["SYSOTI"].Folders["MEP"].Items;
Outlook._MailItem oMep = oItems.Add("ipm.note.mep");
oMep.PropertyAccessor.SetProperty(customPropertyNamespace + "prop1", "SomeText");
oMep.Display(false);

This all works fine, except for the security warning...

This is the redemption code I'm trying to use :

string customPropertyGUID = "{00020329-0000-0000-C000-000000000046}";    
Outlook._Items oItems = oPublicFolder.Folders["Babillards"].Folders["SYSOTI"].Folders["MEP"].Items;
Outlook._MailItem oMep = oItems.Add("ipm.note.mep");
Redemption.SafeMailItem Mep = new Redemption.SafeMailItem();
Mep.Item = oMep;
Mep.set_Fields(Mep.GetIDsFromNames(customPropertyGUID, "prop1"), "SomeText");
oMep.Display(false);

From what I understood this should work. But instead, my mail page opens with all my fields empty. By using OutlookSpy I found out that Redemption creates a new property with this DASL :

http://schemas.microsoft.com/mapi/string/{00020329-0000-0000-C000-000000000046}/prop1/0x0000001F

instead of :

http://schemas.microsoft.com/mapi/string/{00020329-0000-0000-C000-000000000046}/prop1

Can somebody help me? I also tried using the Redemption.MAPIUtils but I ended up with exactly the same result. Is there a way to change a user property by passing the DASL instead of a GUID and ID ?

The two property names are exactly the same - the last part (0x0000001F) is simply property type (= PT_UNICODE). What exactly do you mean by "my mail page opens with all my fields empty"? Do you have a custom form with controls bound to user fields? Also keep in mind that Outlook might not see all the latest changes made with MAPI until the item is completely dereferenced and reopened. Do o use the data after you restart Outlook and reopen the existing item? To avoid Outlook caching problem, try to create the message using Redemption, set the property, and only then open the message using Outlook. Somethiong like the following (off the top of my head):

string customPropertyNamespace = "http://schemas.microsoft.com/mapi/string/{00020329-0000-0000-C000-000000000046}/";    
Outlook.Forlder oFolder = oPublicFolder.Folders["Babillards"].Folders["SYSOTI"].Folders["MEP"];

Redemption.RDOSession session = new RDOSesssion();
session.MAPUIOBJECT = Application.Session.MAPIOBJECT;
Redemption.RDOFolder rFolder = session.(RDOFolder)session.GetRDOObjectfromOutlookObject(oFolder);
Redemption.RDOMail rMsg = rFolder.Items.Add("ipm.note.mep");
rMsg.Fields[customPropertyNamespace + "prop1"] = "SomeText";
rMsg.Save();
//reopen in Outlook and display. Or you can use rMsg.Display()
Outlook._MailItem oMep = Application.Session.GetItemFromID(rMsg.EntryID);
oMep.Display(false);