If you enter pitneybowes.com in the white list, this will whitelist any email address with pitneybowes.com after the @ sign, i.e. email@example.com@pitneybowes.com. - If you enter *pitneybowes.com in the white list, this will whitelist any email address ending in pitneybowes.com, i.e. this will include all the above email addresses but also firstname.lastname@example.org and for instance email@example.com.
Note that it is best to limit the number of wild cards (i.e. * and ?) to optimize performance.