0x80040109 error when Outlook Object Model is used with an IMAP account in Outlook 2013

Symptoms

When you use the Outlook object model to add a UserProperty object to an email message for an IMAP account in Microsoft Outlook 2013, you receive the following error message:

Run time error '-2147221239 (80040109)': The operation cannot be performed because the message has been changed.

Workaround

To work around this issue, close all items after you run the code to add a UserProperty object to an email message. Or, run the code only one time for the same email message. This issue occurs because editing and saving an email message multiple times for an IMAP account is inefficient. When an email message is saved, it must be uploaded to the server as a completely new email message, and the original email message is deleted. If the preview pane is enabled, the original email message remains in memory, whereas the underlying email message is changed because of the multiple uploads.

To reproduce this issue, follow these steps:

1. Select an email message in the message list.

2. Make sure that the preview pane is enabled.

3. Run the following code for the same email message two times in quick succession:

   Function ReproCode()
   Dim oExp As Outlook.Explorer
   Dim oSel As Outlook.Selection
   Dim oMail As Outlook.MailItem
   Dim oProp As UserProperty
   Dim oProps As UserProperties
   
   Set oExp = Application.ActiveExplorer
   Set oSel = oExp.Selection
   
   For iCount = 1 To oSel.Count
   If oSel.Item(iCount).Class = OlObjectClass.olMail Then
   Set oMail = oSel.Item(iCount)
   Set oProps = oMail.UserProperties
   Set oProp = oProps.Add("TextProp", olText, False, 1)
   oProp.Value = "Sample Text"
   oMail.Save
   End If
   Next iCount
   
   Set oExp = Nothing
   Set oSel = Nothing
   Set oMail = Nothing
   Set oProp = Nothing
   Set oProps = Nothing
   
   End Function