Our company has been working on an Outlook AddIn using VSTO which has a
number of issues which we have not been able to resolve yet.

In our .NET addin we have created a couple of custom fields specific to our
application on the Inbox folder. These link to user properties we create on
the mail items. In code when we set the values for these user properties, we
are calling mailItem.Save() both before and after to ensure the values get
persisted.

We are noticing that sometimes the field value in the Inbox is not updating.
Yet if we manually go into the mail item afterwards and save it from the GUI,
it then updates properly. But closing Outlook and re-opening it or changing
folders doesn't make it update. This appears to happen most often on mail
items which have just been forwarded or replied to. We are unsure why the
custom fields don't update sometimes and how to fix this.

Any help much appreciated.