See this URL:
http://www.iea-software.com/emerald/faqs/mailsite.html
> What ver of Serv-U do we need and how do we get that working with Emerald?
You need 2.5 (not a or b) or lower. They instructions on how to set
this up are in the EmerAuth Documentation. You can get the latest
EmerAuth from the /emerald/external/beta directory on our FTP site.
--Dale E. Reed Jr. Emerald and RadiusNT__________________________________________IEA Software, Inc. www.iea-software.com