I've built Enigmail for Seamonkey on Ubuntu for the upcoming 9.04 (Jaunty Jackalope) release, and have therefore moved the files for the older 8.10 release (Intrepid Ibex).
Here are the URLs for both releases :
All files are signed using my key id=0xA622D452 which can be downloaded from here or by using one of the OpenSKS keyservers (such as keyserver.rainydayz.org).
