I do not understand what’s the problem, they got the mail from everyone about the preferred batch, they should have a list about batches and customers
i.e.
10k total customer with their preference stored
purism reading the customers preference will make a list like
batch A (order #12345, order #345 …)
batch B (order #54321, order #543 …)
and so on for every batch
when they have this list filled my desire is to know in which batch i belong