VERP sucks

Last year I bought a phone for Abhijit, who prefers something small and simple and couldn't find it. I could, at €17, so I ordered one and sent it to him, and have been spammed ever since. Not a problem, I can reject mail faster than the spammers can photoshop boobs for their pictures.

But today I received a friendly message pointing out that they've been unable to send me important mail, and would I please take corrective action. Reading, it became clear that they use VERP, and therefore don't know anything about the rejection. Their VERP software is told about, and ignores —

1. the rejection's machine-readable reason code (5.7.1 in this case — The sender is not authorized to send to the destination),
2. the rejecter's identity (the addressee in my case),
3. the rejecter's human-readable message (Bitte kein Spam) and
4. everything else except my email address.

VERP is supposed to be the state of the art? How can anyone possibly think so?