In step 5, one can indicate what a guest's history must satisfy to qualify for a mailing selection. (Step 5 only affects the reservations that meet the criteria of step 4). For example, that X amount of sales has been generated by the guest's stay in the hotel, or that the total number of nights that the guest has spent in the hotel is more or less than X.
One can proceed to Mailing wizard step 6 after these criteria have also been entered according to one's wishes.