Quoting Jon Schewe <jpschewe at mtu.net>:

> I've got a postfix mailserver that's getting a lot of spam (who
> doesn't).  The problem I'm trying to address is that some spammer sends
> a messages to xyz at mydomain.com and xyz doesn't exist on my system, so
> postfix generates a bounce message.  However the reply-to in the
> original message doesn't exist either, so the bounce, bounces back and
> eventually ends up in the postmaster mailbox.  Is there a way to tell
> postfix to reject the message right away when the spammer tries to send
> it, so that the bounce message isn't generated?  Or to just give up on
> bounced bounces?
> 
That seems really odd. I would think that the default for an MTA would be to
reject mail which does not have an intended recipient. I am not familiar with
Postfix config, but a quick google indicates you should look at your config to
see if you have something like so:
your_domain.com anything
Which would apparently accept anything sent to your_domain.com.

Also, is there a secondary MX for your domain that might be catching some mail
and forwarding it to you? I used to have some issues with that at work.
Occasionally the secondary MX would get some mail and attempt to forward it to
our server. Our server would reject it, the secondary MX would bounce it, and
the apparent sending domain would bounce the bounce back to us. I stopped using
a secondary MX after the virus bounces got really annoying, no need for it
really if you have a somewhat reliable mail setup.

Josh

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