ST> What is a "Cron Poll" ?

Dumb answer: See Config->Polls->Periodical. The 'cron' function is taken from
*nix and uses this format:

Minute Hour Day Mth DayOfWeek
------ ---- --- --- ---------
x x x x x

So, an entry like this: "45 23 * * * | 1:275/311" would cause a daily poll to
your system at 23:45. (There is a short form also: "45 23 | 1:275/311" where
the asterisks are considered superfluous.) Mind you, one of the options in the
manager stops ad-hoc polling on outbound mail (with exceptions inherent in BSO)
so there would only be a single poll every day. I use one of those to call a
node in zone2 daily.