By default, Pine automatically checks for new mail every 2.5
    minutes (150 seconds). This interval is settable per user as
    the MAIL-CHECK-INTERVAL configuration option (unless the system
    manager choose to fix its value in the PINE.CONF-FIXED file). You
    can also force a refresh of the folder by pressing the DOWN arrow
    key four times at the last message of the Index screen or by
    pressing CTRL/L. A folder is also refreshed whenever you expunge
    it. When you force a check, and you have no new mail, Pine will
    report the last message as new mail even though it is not new.