I have found a few damaged Winchester shells but just tossed them. For their price, usually a bit lower than the other brands, I just forget it. In fact, I just opened a box that has a really oversized hull. No way it can fit a chamber unless it is hammered in. It ain't worth the bother of letting Winchester know what they already are aware of. Their QC is like most other companies now. Non-existent, it seems.
I have found very few Federal or Remington shells that needed to be tossed. Remington ammo has extra hard primers that some guns have FTFs with. I just toss them and forget about it.
As to emailing them, I have no idea. Since their gun and ammo divisions have separated, it may be next to impossible. I'll check my research books and see what I can find but it won't be worth the stamp if you have to snail mail it.