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Date:      Sun, 13 Feb 2005 17:56:42 -0800
From:      "Noah Davidson" <NoahD@oopz.com>
To:        <bv@wjv.com>, <freebsd-isp@freebsd.org>
Subject:   RE: Sendmail question
Message-ID:  <1BC9C5447DEF1F4FBE3927A31D6B540404DC09@gehrig.hall.oopz.com>

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This is a backup mail server.  The primary mail server is an Exchange =
2003 server.  So when mail is sent to invaliduser@bdomain.com then this =
server sends the mail to the exchange server that is responsible for =
handling the mail for domain.com.  Since the user does not exist it =
bounces the mail.  Then the root alias gets a copy of the bounced mail.  =
Is there any way to prevent this from happening?  This server should =
just queue the mail for the exchange server until the exchange server is =
available.
=20
Thanks
Noah Davidson

________________________________

From: owner-freebsd-isp@freebsd.org on behalf of Bill Vermillion
Sent: Sun 2/13/2005 5:42 PM
To: freebsd-isp@freebsd.org
Subject: Re: Sendmail question



I know you'll find this hard to believe, but on Sun, Feb 13, 2005 at =
23:13 ,
Suporte Matik actually admitted to saying:

> On Sunday 13 February 2005 22:46, Noah Davidson wrote:
>
> > The only problem with that approach is that this is a back up
> > server and the users may not be able to know of all of the
> > users. Is there any way to not have all of these bounced mail
> > go to the postmaster / root account.


> sendmail should reject mail for nonexistent users by default
> and not forward to root unless you have any strange alias for
> all but you say bounced mail what confuses me a little bit, but
> anyway, isn't it that your systema accounts are exploited by
> the spammers ? so if having 10 domains you may get 10 spams for
> tty in your root mailbox, to prevent you may try this in your
> access:

> tty@    ERROR:"4.2.2:450 No such user here."

> and so on for each systema account and rebuild the access.db and
> probably your headache goes away

The problem I have is that when mail is bounced back mail from
spammers often comes from forged addresses and I get emails
from the far site indicating there are unknown users.

So I find routing noexistant users to /dev/null is more productive.
While it's not exactly the best way to do it, there are so many
bogus addresses sending mail I haven't found a good alternative.

One site we handle has one of those strong standalone names that
don't require any advertising to come up #1 on google or msn and
when it finally hit 300,000 spams/day for that one domain I took
out the MX records.

I use the access.db for blocking known places and I won't send
anything back at all - I used the DISCARD verb as sending messages
back does nothing but generate more traffic.

> >
> > ________________________________
> >
> > From: Bill Vermillion [mailto:bv@wjv.com]
> > Sent: Sun 2/13/2005 2:30 PM
> > To: Noah Davidson
> > Cc: FreeBSD-ISP List
> > Subject: Re: Sendmail question
> >
> >
> >
> > Ashes to ashes, and DOS to DOS Noah Davidson was heard to say
> >
> > on or about Sun, Feb 13, 2005 at 14:10 :
> > > I have set up a new FreeBSD box as mainly a backup mail server,
> > > although it is primary for a couple of domains. It is running
> > > sendmail 8.13.3 and it works fine, except for all the spam that
> > > is being sent to it to bad email addresses. I have aliased
> > > the root account to an email group on another server so that
> > > someone reads the root mail. The problem is that all the mail
> > > that spammers are sending to address that do not exist get
> > > bounced and the root account a notification (I believe it
> > > is the postmaster alias which is aliased to root). Is there
> > > any way to not have these notifications sent out. They are
> > > filling up the mail boxes. I just want the return to sender, but
> > > not to the root / postmaster as well. I have tried using the
> > > confCOPY_ERRORS_TO in my .mc file, but that just sends it to an
> > > additional account as well.
> >
> > Making assumptions that your sendmail is receiving bogus mail
> > for accounts that you have sendmail receive here is approach you
> > can take.
> >
> > Assume you have domains  a.com b.com and c.com and your
> > local-host-names has those.
> >
> > Then you need to find out what users you have for each domain
> >
> > If you have curly larry and moe on a.com and no one else, then you
> > can build a virtualusrtable that looks like this.
> >
> > curly@a.com     curly
> > larry@a.com     larry
> > moe@a.com       moe
> > @a.com          nouser
> >
> > And the accnount 'nouser' will be in your /etc/mail/aliases
> > file and will look like this:
> >
> > nouser:  /dev/null
> >
> > Run make in /etc/mail to create virtusertable.db and aliases.db
> > and that should get rid of the bogus names going to root.
> >
> > I find the virtualusertable to be quite handy for elminating a lot
> > of junk.   It will only be a problem if you have a large user
> > base or lots of domains.
> >
> > Bill
> > --
> > Bill Vermillion - bv @ wjv . com
> >
> >
> > _______________________________________________
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> > http://lists.freebsd.org/mailman/listinfo/freebsd-isp
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>
> --
>
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--
Bill Vermillion - bv @ wjv . com
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