I am certain I should have realized this sooner, but it does appear that any changes made to the postgrey white-lists are overwritten during an upgrade. With this in mine, would be be worth considering a new area in the admin panel to allow you to enter whitelist entries that could be merged into the default one installed into the system? The alternative would be to allow postgrey to pickup two whitelists, but on first glance it does not appear that can be done.
It has actually been causing some issues with senders who do not have compliant mail servers, and it also seems that upgrading wipes out anything postgrey has learned over time and everyone starts getting greylisted again.
It is possible I am incorrect in some of this, and it is really a first blush inquiry at this point, but if someone knows more than I it may save me some time and headache.
I would love some thoughts on this.