EDIT: The newest version of Quote Message Service can be found on Microsoft Exchange Server 2003 Tools site.
Yesterday I uploaded the 1.1.0 release of the Quota Message Service, which allows you to send custom messages to users who exceed their quota. New to this build - setup improvements, including logging via MSI of setup actions and failures, a fix for high CPU utilization/log generation, and some minor format changes for the "Difference" inserts.
http://workspaces.gotdotnet.com/quotamsgsvc
Note - you are not required to join the workspace to download, use, view the source, or post questions about the service. As always, the documentation is installed to the same directory as the service.
Updated Jul 01, 2019
Version 2.0The_Exchange_Team
Microsoft
Joined April 19, 2019
Exchange Team Blog
You Had Me at EHLO.