I've installed Post Office and the associated pre-requisites and it appears on the Plugins configuration page but only Info is selectable, i.e. the Settings button doesn't appear.
Any clues as to what I've not done/done wrong would be welcome?
Thanks
Reported on Movable Type 4.2

If memory serves, Post Office doesn't have any system-configurable settings. Go to the blog-level and you'll find the Settings there.