What happens when you also add the MessageDisposition attribute?
//MessageDisposition is one of:
//SaveOnly The item is updated and saved back to its current folder.
// SendOnly The item is updated and sent but no copy is saved.
//SendAndSaveCopy The item is updated and a copy is saved in the folder // identified by the SavedItemFolderId element.
$UpdateItem->MessageDisposition = "SaveOnly";
Also, if you got CreateItem to work, I'm completely stumped on that one. Here's my PHP code which will send a message with a blank body. But as soon as I add the body text, I get a schema error.
$CreateItem->MessageDisposition = "SendAndSaveCopy";
$CreateItem->SavedItemFolderId->DistinguisedFolderId->Id = "sentitems";
$CreateItem->Items->Message->ItemClass = "IPM.Note";
$CreateItem->Items->Message->Subject = "My Subject";
$CreateItem->Items->Message->Body->BodyType = "Text";
// Adding this line for the body throws schema error
$CreateItem->Items->Message->Body = "Body Text";