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MessageHandler refuses to install, if you specify directories in the installations wizard,

• which do not exist! 
  Inspect the installation logfile and search for error messages

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• like 

  No Format
  MSI (c) (7C:54) [14:32:12:501]: Note: 1: 1314 2: /Program Files/Sedexclient/interface MSI (c) (7C:54) [14:32:15:251]: Product: Open eGov MessageHandler -- Error 1314. The specified path '/Program Files/Sedexclient/interface' is unavailable.

• to which the chosen Service User Account does not have sufficient access rights. In this case the MH service will refuse to start in the installation process and the installation fails.
  To diagnose this situation, inspect the file c:\Program Files (x86)\Open eGov MessageHandler\log\message-handler.log , while the MSI Installer still displays this error dialog:
  
  Image Added

MSI Installer fails to install or uninstall MessageHandler

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