I find it useful when using Hudson to queue up deployments across a cluster of
servers to send a pre-build(pre-deploy in my case) email as well as a
post-build(post-deploy) email. Email-ext can be easily extended via my patch to
enable an additional, pre-build trigger.
Note that I had to also tweak SuccessTrigger because it was firing even when the
build had not really begun yet since it was only looking at the result status
for each build. Since a build that hasn't started yet always has a result of
Success it always fired. No other triggers have this problem because they all
look for results other than Success.