the `previous'/`next' buttons in the toolbar have the wrong label: they do not go to the previous or next message, but to the previous or next *unread* message. the tooltip does say that, but the label itself only states `previous'/`next'. so, i'd encourage to rename the labels or change the semantics so that their behavior follows the `principle of least surprise'.
I confirm but will not change. Text will too big in toolbar.
another more reasonable solution would be to change the semantics of the actions, to the labels: go to next/previous message instead of next/previous unread ... then it does what the label tells and the buttons are usable for people who browse mailing list archives ...