Sometimes, awesome:

$split = $address -split "@"
$address = ([regex]"\w+").Replace($split[0], { $args[0].ToString().Substring(0, 1).ToUpper() + $args[0].ToString().Substring(1).ToLower() }) + "@" + $split[1]

Handles james.o’tootle@mydomain.com -> James.O’Tootle@mydomain.com.  Does not handle james.mcnally@hardwork.com -> James.McNally@hardwork.com, though… sorry but semantic parsing is beyond the scope of this blog 🙂