We upgraded from version 13.2 to version 15 because some of our clients were starting to have their Outlook 2013 crash when it would use activesync to sync their calendar.
We created a backup, stopped IIS7, uninstalled Smartermail, ran version 15 installer, started IIS7 made sure NET version of the Application Pool to .NET 4.0, restarted IIS7.
We are getting the following error when you try and use the Smartermail interface.
Server Error in '/' Application.
Description: An error occurred during the parsing of a resource required to service this request. Please review the following specific parse error details and modify your source file appropriately.
Parser Error Message: Unknown server tag 'STWC:GlobalizedLabel'.
Line 17: <asp:Content ID="Content1" ContentPlaceHolderID="MPH" runat="server">
Line 18: <h2>
Line 19: <STWC:GlobalizedLabel ResourceIDGlobal="@EmailAddress" runat="server" />
Line 20: <small>
Line 21: <STWC:GlobalizedLabel ResourceIDPage="Example" runat="server" /></small>
Source File: /Login.aspx Line: 19
Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.34280