Most scripts don't allow for rejection emails. Mine does so I send them, and usually give a reason as long as there's only one or two. I've known the frustration of the the unknown decline (I think it even has a tomb in Arlington

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However, I see so many repeat errors...the worst one being the same template submitted over and over again (sometimes more than once in a single day) that I give decline explanations a up to 3 times for the same thing then blacklist. I've always said, if you can't be bothered to read a rejection email that says "Fetish Philes LINK DECLINED WITH EXPLANATION" in the subject line and keep submitting the exact same crap, then I can't be bothered to keep reviewing your sites.
I'm considering going to the "ask me at GG & Jim" program, simply because I get so many submits now and the overall quality is going down to the point where writing individual reasons in each one is starting to take up a LOT of time. I'll still send the decline emails if I go that route, but they'll just say to come ask me here.
BTW, I once had a submitter actually THREATEN TO STOP SUBMITTING if I didn't list his site.

Yup buddy, that's how you get listed....