I can't comment specifically on Google but as a general rule I have found that such non receipt issues are usually down to false positives in the recipeient's spam filtering.

First, I suggest to stop showing Adsense ads until this issue is resolved. Registering a "4 figures amount every month" with no way to actually get to the money is a bit, um, risky, don't you think?

Especially when you don't get a response from the friendly folks at The Plex.

Problem with the PIN is - the PIN comes in a postcard format and looks like a (badly designed) promotion, really unimportant. (Well, at least that was the case when we received our PIN three years ago.) I could imagine that this gets easily overlooked and goes straight to the bin.

Thanks ZETT.. I know the PIN format even i have got many account running with no issue. this is the only case.. thanks for suggestion.. i should stop showing ads.. but i am not sure why google is sleeping on this matter..

One more thing, little on the other part but adsense only. today i found my 1200 pages which had adsense my code, are changed with the different channel but my publisher ID. Channel is not mine but the PUB ID is mine. How would google treat this as..? and to whom the money will go to..?

I doubt that there is somebody in the team only, new to adsense and have changed it intentionally but forgot to change the PUB id. Is it possible for us to ask google to inform us whose channel is this and belongs to whome and in which part of the world..? Will google entertain these kind of issue.?

I'd ask Google as nicely as you can and make it as short as you can...don't bother the Google monster too much or you will make it angry.