Yes, I understand that if I'm pretending to be Dovecot that I should talk like Dovecot or at least follow the protocol as documented in Dovecot's Wiki. The protocol error in my implementation is already fixed.
It's just that Postfix never ever crashed on me before and I believe that it should never crash, even when facing protocol errors in talking to an "internal" service. Therefore I reported this issue with what I consider as much information as possible to make it easy enough for you to fix. I take the patch at the bottom of your email as "this patch is included in the next release" and thus consider this case closed. Thank you. Best regards Tim Düsterhus