Hello,

my question isn't that much ASInet related ...

I use Mercury as a mail server and a program written in Xbase++ to 
check incoming emails (block spam on the "FROM:" information and the 
content of the message). Now I would like to bounce unwanted messages 
to the sender pretending that I can't be found on my mail server ...

Since the message is retrieved and deleted on the external mail server, 
I need to change the incoming message. Has someone a nice explanation 
of how to do it (I have an example, but need some advice)?

Kind regards,

Georg S. Lorrig

Georg S. Lorrig wrote:

> Now I would like to bounce unwanted messages
> to the sender pretending that I can't be found on my mail server ...

This is most likely useless and a waste of bandwidth and programming
capacity on your side, since most spammers do not process any bounces.

You will get more information regarding this topic at

news.admin.net-abuse.email
or
de.admin.net-abuse.email (if you prefer the German language in this case)

regards
Thomas Braun

web: www.software-braun.de / email: nospam@wegasoft.de
If you need to send email, substitute "nospam" with my initials
since the spam account is not checked on a regular basis.
Xbase++ FAQ : faq.xbasecentral.net

Hi, Thomas -

I get a lot of junk from companies directly. At least it would be a good 
test to pick one or two and see if they stop sending.

Thank you for the information,

Georg

In article <3e55ef96$1@asgcom.alaska-software.com>, Thomas Braun wrote:
> Newsgroups: alaska-software.news.ASINet
> Subject: Re: How to bounce a mail message?
> From: Thomas Braun <nospam@wegasoft.de>
> Reply-To: tb@wegasoft.de
> Date: 21 Feb 2003 10:21:26 +0100
> 
> Georg S. Lorrig wrote:
> 
> > Now I would like to bounce unwanted messages
> > to the sender pretending that I can't be found on my mail server ...
> 
> This is most likely useless and a waste of bandwidth and programming
> capacity on your side, since most spammers do not process any bounces.
> 
> You will get more information regarding this topic at
> 
> news.admin.net-abuse.email
> or
> de.admin.net-abuse.email (if you prefer the German language in this case)
> 
> regards
> Thomas Braun
>

>I use Mercury as a mail server and a program written in Xbase++ to 
>check incoming emails (block spam on the "FROM:" information and the 
>content of the message). Now I would like to bounce unwanted messages 
>to the sender pretending that I can't be found on my mail server ...
>
>Since the message is retrieved and deleted on the external mail server, 
>I need to change the incoming message. Has someone a nice explanation 
>of how to do it (I have an example, but need some advice)?

Technically, you can't bounce a mail once it has been received (and if
it is on your mail server, then it has been received).  Consider the
following:

Client -> Relay [-> Relay] -> Mailbox

The Client is the sending mail client.

Relay is one or more mail relay agents. Typically, these are domain
(ISP) mailservers which allow relaying.  Note that most mailservers do
not allow relaying anymore.

Mailbox is the target mailserver which has a mailbox which matches the
addressee of the message.  Once it reaches this mailbox, the mail has
been delivered.  It is not necessary for a mail client to download the
mail for it to be considered delivered.  Note that under RFC822, where
a specific mailbox is not found for a given servers domain, the mail
should either be rejected out of hand or delivered to the postmaster
mailbox.

Due to spamming, most mailservers operate blacklists, and refuse to
accept mail coming from specified domains or routed (relayed) through
specific servers.  The upshot of this is that to void being placed on
someone else's blacklist, the mailserver will refuse to relay mail.

Enter MX routing.  With MX routing, a mail address is deconstructed to
discover it's domain, and the IP address for that domain is recovered
from a DNS search.  This allows the mail to be delivered directly to
the mailserver holding the mailbox.  If you look at the header of any
mailmessage you receive, you will be unlikely to see more than 2
mail-relayers listed in the routing information (their outbound router
and your inbound router).  If you have additional routing information,
it is likely that the route taken required your message to cross a
private-network firewall and access a local DNS.

In this scenario, a message will be delivered if MX routing fails.  To
return a message that looks like it has been bounced without the
corresponding delivery failure message from the sending router will be
suspicious.  To perform a proper spoof, you would also need to tinker
with the header routing info, which is a no-no.

Since most spam mail addresses automatically junk inbound mail (or are
in fact fictitious addresses), it is a waste of time trying to return
mail since most of it will come back at you again when it it fails to
deliver.

You are far better off just junking spam.

Regards,

Phil Ide

Xbase++ FAQ
current release: 8,  Monday 4th February 2002, 14:54
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