Email question

[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

abuse at domain.tld          jakemch
webmaster at domain.tld jakemch
jake at domain.tld             jakemch
otherone at domain.tld     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


-- 
Alexander Dalloz | Enger, Germany | GPG key 1024D/ED695653 1999-07-13
Fedora GNU/Linux Core 2 (Tettnang) kernel 2.6.6-1.435.2.3.ad.umlsmp 
Serendipity 18:40:09 up 3 days, 3:46, load average: 0.05, 0.10, 0.18 
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