In order to verify if the Windows MAPI subsystem is installed, Spectrum checks the values of the following registry keys prior to the installation routine running:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Messaging Subsystem
If the expected values are not found, Spectrum will issue the following error:
Warning:Windows Messaging Subsystem is not installed on this system. Email will not work with SPECTRUM applications
Follow the steps in Method 2 - Verify The Registry Settings - in the following MS article:
If you are using a utility such as Microsoft Mail which will also install the MAPI subsystem you may still see the above error.
Applications such as Microsoft Mail while installing MAPI do not update this registry key and therefore you may still see the above error message even though the install completes successfully and all mail functions work.
Note: Microsoft no longer support Microsoft Mail.