Dovecot Sieve and Postfix header_checks Issue

[Klaipedaville on Google]

>Alex:
>One *very* convincing argument not to send an *email* response (reject at SMTP is fine) is that it is very likely indeed you'll end up on an RBL yourself for doing this. It happened to us when we were still bouncing (probably >about 8-10 years ago). It was the main reason we stopped.
>
>Reindl,
>I respecfully disagree with (a) at least for the UK. It may be the case in Germany but I'll be damned if I'm going to give up on my Mailscanner - tuned over the years enough that we've never had a legit mail get canned.
>
>Anyway, that's enough for me otherwise this is going to turn into a flamewar rather than informational. 
It is really convincing but if you do it right I guess you should be safe .

Well, bouncing it all bluntly like shooting from a machine gun absolutely everywhere at random will certainly put you on RBL. How about checking it first if the sender's email address really exists and only then either bounce back (it the address exists) or do not bounce it back if it doesn't. You were the one to tell me in your previous messages to comply with RFC first that is to check for forged envelope senders first. That’s why I have been bouncing it back (rejecting) for the past 4 years and have never ever hit any RBLs at all.