Sam Varshavchik wrote:
> Bowie Bailey writes:
> > Sam Varshavchik wrote:
> > > 
> > > maildrop is using SENDMAIL, however maildrop is also explicitly
> > > adding the -f "" flag also.  Originally, this change was added to
> > > prevent maildrop from generating backscatter; but now that Courier
> > > has a real backscatter suppression filter, this is really no
> > > longer needed. 
> > > 
> > > However, you can replace "!<address>" with "| $SENDMAIL
> > > <address>", and get the same results.
> > 
> > Things are starting to make sense now.  That behavior should either
> > be removed (if it is not needed), or documented so it doesn't
> > confuse anyone else.  Or possibly you could check to see if the
> > $SENDMAIL variable already set a -f flag and only do -f "" if the
> > flag is not already set. 
> > 
> > I did play around with the "| $SENDMAIL" construct and it works
> > fine. Unfortunately, that means I have to modify about 200
> > .mailfilter files as well as my program that maintains the
> > accounts.  Can I modify the code to remove this behavior?  If so,
> > where do I look? 
> 
> maildrop/deliver.C:
> 
>                         cmdbuf=sendmail;
> 
>                         cmdbuf += " -f '' ";
> 
> Replace this with
> 
> cmdbuf += " ";

Perfect.  I'll give this a try.

> I'm still waffling as to the right solution for this.  There are
> three basic options -- pass along the original $SENDER, as you're
> doing.  I earlier believe that if that bounced, the backscatter will
> get eaten, but I was wrong.  The forward message is really a new
> message that originates locally, whose contents happen to be the same
> as the original message, and its any bounce is not seen as
> backscatter.  The second option is to set the return address to a
> null, thus all bounces get discarded -- the current behavior. The
> third option is to use the address doing the forwarding as the return
> address, but this may result in mail loops. 

I'm not sure I understand why this would be considered backscatter.
This is what I see:

- Someone sends mail to one of my users
- I use maildrop to forward that mail to the user's preferred account
- Any bounces generated at any point in the chain need to go back to
  the original sender so that he knows the message was not received.

> Mail forwarding has always been clumsy.

Agreed.  And now, with SPF, it is even worse.  Unfortunately, I don't
see the need for it going away anytime soon.  My problem is that I
host web and mail services for our customers' domains.  Quite a few of
them want me to forward mail from their domain accounts over to their
ISP account.

-- 
Bowie


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