Email question

[Jake McHenry]

Hi everyone,

is there a way I can set up sendmail so that no emails bounce? if someone gets a wrong address or is just trying to find account names, could those emails be set up in an alias or something to be sent to my address?

Thanks,
Jake McHenry

MIS Coordinator
Nittany Travel
http://www.nittanytravel.com
570.748.6611 x108

[SternData]

On Thu, 29 Jul 2004 12:16:32 -0400, "Jake McHenry" 
wrote:
> Hi everyone,
>
> is there a way I can set up sendmail so that no emails bounce? if someone gets a wrong address or is just trying to find account names, could those emails be set up in an alias or something to be sent to my address?

============

http://www.sendmail.org/~ca/email/lfaq.html#LUSER

How to route mail to unknown users to one account?
sendmail 8 has a feature to route all mail which ends up as local on the
system but isn't a valid account (or alias), to another system (the so-called
LUSER_RELAY), see cf/README (from 8.8). However, this feature is
disrecommended, since it can break ``working'' addresses if you introduce new
local users.

If you want to route all mail to unknown users to one account (instead of
giving the standard error reply), you can put in your .mc file the following:

define(`LUSER_RELAY',`local:[e-mail]')

or in some cases:

define(`LUSER_RELAY',`local:someuser')

Something similar can be accomplished for virtual domains.

==============

--
   Steve

[Alexander Dalloz]

Am Do, den 29.07.2004 schrieb Jake McHenry um 18:16:
> is there a way I can set up sendmail so that no emails bounce? if someone gets a wrong address
> or is just trying to find account names, could those emails be set up in an alias or something to be
> sent to my address?
> Jake McHenry

Sure you can, but non delivery notifications to the sender have their
sense. Account harvesters should be catched differently.

To get all mail for non existent user accounts (mail addresses) you can
use a so called catchall adress: create /etc/mail/virtusertable and
insert the pairs of valid addresses, looks like

[e-mail]          jakemch
[e-mail] jakemch
[e-mail]             jakemch
[e-mail]     otheruser
@domain.tld                    eatitall

where "eatitall" is an account you creates and where all the non fitting
mail for @domain.tld goes. After the virtusertable file is complete you
have to run "make -C /etc/mail". A complete restart of the Sendmail
service is not necessary.

To stop valid address harvesters you should make use of

define(`confBAD_RCPT_THROTTLE',`3')dnl
define(`confMAX_RCPTS_PER_MESSAGE',`6')dnl

in the sendmail.mc file. The values 3 and 6 are examples here which I
use. A change of the sendmail.mc file must be followed by a "service
sendmail restart". Be sure you have the sendmail-cf package installed.
In addition to these Sendmail settings you can use iptables to block
harvester. Use a tool like swatch to let your maillog observe and
automatically react with an iptable reject rule for source addresses
from where illegal mail attempts come from. Just be very careful to not
be totally blocked by someone using this automatic setting for a self
cause DoS.

Alexander

[Jake McHenry]

what are the 3 and 6 examples for in your post? I added this into my mc and
restarted sendmail, I tried sending 8 emails to an invalid user and all 8
got receipts back.

I understand the use of the return receipts, but from logwatch, there are
roughly 100 invalids a day. I need this to stop.

Thanks,
Jake McHenry

MIS Coordinator
Nittany Travel
http://www.nittanytravel.com
570.748.6611 x108

----- Original Message ----- 
From: "Alexander Dalloz" 
To: "For users of Fedora Core releases" 
Sent: Thursday, July 29, 2004 12:49 PM
Subject: Re: Email question
> -- 
> fedora-list mailing list
> [e-mail]
> To unsubscribe: http://www.redhat.com/mailman/listinfo/fedora-list

[Alexander Dalloz]

Am Do, den 29.07.2004 schrieb Jake McHenry um 22:34:
> what are the 3 and 6 examples for in your post? I added this into my mc and
> restarted sendmail, I tried sending 8 emails to an invalid user and all 8
> got receipts back.
>
> I understand the use of the return receipts, but from logwatch, there are
> roughly 100 invalids a day. I need this to stop.
> Jake McHenry
> define(`confBAD_RCPT_THROTTLE',`3')dnl
> define(`confMAX_RCPTS_PER_MESSAGE',`6')dnl

See the cf/README i.e. on:
http://www.sendmail.org/m4/tweaking_config.html. I didn't say the sender
does not get any DSN (failed receipe) back. The settings just slow down
things for dictionary attacks.

Alexander

[Jake McHenry]

----- Original Message ----- 
From: "Alexander Dalloz" 
To: "For users of Fedora Core releases" 
Sent: Thursday, July 29, 2004 5:16 PM
Subject: Re: Email question
> -- 
> fedora-list mailing list
> [e-mail]
> To unsubscribe: http://www.redhat.com/mailman/listinfo/fedora-list

Ok, so basically I can't keep someone from doing this unless I turn it off
all together, which would not allow a legitimate user to get a bounce back.

[Alexander Dalloz]

Am Do, den 29.07.2004 schrieb Jake McHenry um 23:46:
> Ok, so basically I can't keep someone from doing this unless I turn it off
> all together, which would not allow a legitimate user to get a bounce back.

At least as long as you do not invent an AI routine which can
distinguish between legitimate users and clever SPAMmers ;)

Of course you can enhance Sendmail with a milter application like
MimeDefang which has then Perl program code which suppresses DSN notify
mails when it thinks to recognize SPAM attempts. Anti-SPAM fighting is a
never ending story, you as mailserver admin are ever followed by the
flexible SPAM troupers,

The easiest way is to observe the maillog and based on this logging to
run a cronjob which blocks the SPAMmers by iptables rules. I can send
you a working script for that if you like.

Alexander

[Jake McHenry]

I'm not running iptables ...  on the old setup I had mailscanner running and
another utility that gave me stats on email that could add spammers to the
access db, maybe I'll just configure all that again. The only problem was
some addresses entered into the access db were legitimate people. Can anyone
recommend a better solution?

Thanks,
Jake McHenry

MIS Coordinator
Nittany Travel
http://www.nittanytravel.com
570.748.6611 x108

----- Original Message ----- 
From: "Alexander Dalloz" 
To: "For users of Fedora Core releases" 
Sent: Thursday, July 29, 2004 5:56 PM
Subject: Re: Email question
> -- 
> fedora-list mailing list
> [e-mail]
> To unsubscribe: http://www.redhat.com/mailman/listinfo/fedora-list