Can I install MailSpring in a different location, e.g. on P:\ instead of C:?
Unfortunately, no — our Windows installer is built on Squirrel.Windows (via electron-winstaller), which is a one-click installer with no directory-selection step; it always installs to %LocalAppData%\Mailspring, under your user profile on the C: drive. There’s no config flag to redirect that without swapping to a different installer framework entirely, which isn’t in the works right now. Sorry it’s not more flexible here.