You can confim whether DMI has been installed on your machine or not using Mail Preferences.
1. Launch Mail.
2. Choose Mail > Preferences...
If DMI has been installed on your machine, the Preferences window toolbar shows the Daylite icon.

If Daylite icon does not appear, this means DMI is not installed on the user's account in this machine. DMI integrates with Mail for each user. Hence, it should be installed seperately for each user that needs to use it.
DMI can be downloaded and installed seperately at
http://www.marketcircle.com/downloads/dmi.htmlOnce installed, DMI will automatically load when Mail is relaunched.