In general, I think mail delivery is very reliable. But given the volume, there will be outliers. Even if we assumed 99.9999% reliability (a hypothetical number), given that they sort 300MM pieces per day, 300 pieces per day will be affected.
If you have the money, you should try an experiment: mail a large number of ballot-like pieces from different mailboxes all over the county (say, 10,000 letters) and see how many reach the destination. Sure, it'll cost $5K, but you may have a better answer.
If you have the money, you should try an experiment: mail a large number of ballot-like pieces from different mailboxes all over the county (say, 10,000 letters) and see how many reach the destination. Sure, it'll cost $5K, but you may have a better answer.