----- Original Message -----
From: "Ian Eiloart" <iane@???>
To: <exim.ml@???>
Cc: <exim-users@???>
Sent: Monday, June 28, 2010 6:48 AM
Subject: Re: [exim] listed at Backscatterer.org
>
>
> --On 25 June 2010 13:56:12 +0100 Ron White <exim.ml@???> wrote:
>
>> On Fri, 2010-06-25 at 11:28 +0100, Ian Eiloart wrote:
>>> --On 24 June 2010 09:43:40 +0000 Kebba Foon <kebba.foon@???> wrote:
>>>
>>> >
>>> > Backscatterer - Why it is abusive and how to stop your system doing so
>>> >
>>> > Email servers should be configured to provide Non-Delivery Reports
>>> > (bounces) to local users only.
>>> > Unacceptable email from anywhere else should be rejected.
>>> >
>>>
>>> This is silly advice. It should be quite acceptable to bounce email that
>>> has an SPF pass, or that has a valid DKIM signature (provided the return
>>> path domain matches a signed From header domain). In both cases, if
>>> you're creating collateral spam, then that's the fault of the domain
>>> operator.
>>>
>> There is probably a bit of a translation issue there as backscatter.org
>> is part of Dirk & Claus 'UCEProtect' stable of blocklists.
>>
>> My personal opinion is you should never accept mail that you cannot
>> deliver to a user and in such a scenario it should be rejected at SMTP
>> time - not after a 250 is given and (any/the) MTA decides it does not
>> want it for whatever reason. Exim is very flexible and its brilliant
>> ACL's can pretty much reduce backscatter to zero if configured
>> correctly.
>
> Well, the backscatter issue means that we have no choice but to try to do
> that. But that's a bad thing. It would be a much better world in which we
> were able to accept such messages, and then generate a bounce. Why?
> Because
> bounce messages have the potential to be more user-friendly.
>
> I believe that with improved email authentication (SPF, DKIM, etc), we'll
> one day be able to revive the bounce message.
>
>
> --
> Ian Eiloart
> IT Services, University of Sussex
> 01273-873148 x3148
> For new support requests, see http://www.sussex.ac.uk/its/help/
>
>
>
> --
> ## List details at http://lists.exim.org/mailman/listinfo/exim-users
> ## Exim details at http://www.exim.org/
> ## Please use the Wiki with this list - http://wiki.exim.org/
>
>
Hi all,
I was happy to see someone else start this thread :-)
I have been researching and tinkering to no avail on the backscatter
issue. Trying to make sure I am not the source, or the recipient of
backscatter. backscatterer.org has not helped as occasionally my server have
been listed.
I am attaching a copy of my configure script hoping someone might have
some suggestions as to how to curb/eliminate backscatter.
My server is a virtual setup, domains listed in /etc/domains, real unix
user mapped to domains through /etc/domains_users, virtual users (for each
domain) listed in a password file in /etc/virtual/<domain>/passwd, aliases
listed in /home/<domain>/mail/aliases. The server is still sending mail
through the base server name (FQDNS)
Also, feel free to crituque the whole config:
######################################################################
# MAIN CONFIGURATION SETTINGS #
######################################################################
primary_hostname = <mydomain>
domainlist relay_to_domains =
domainlist local_domains = /etc/virtual/domains
domainlist filtered_domains = /etc/virtual/filtered_domains
hostlist filtering_hosts = /etc/virtual/filtering_hosts
hostlist relay_from_hosts = /etc/virtual/domains
hostlist blacklisted_domains = /etc/virtual/blacklist
hostlist spf_bypass = /etc/virtual/spf_bypass
hostlist whitelist = /etc/virtual/whitelist
acl_smtp_rcpt = acl_check_rcpt
trusted_users = mailnull:root:webmail:www
exim_user = mailnull
exim_group = mail
never_users =
host_lookup = *
rfc1413_hosts = *
rfc1413_query_timeout = 5s
ignore_bounce_errors_after = 0s
timeout_frozen_after = 0s
auto_thaw = 6h
return_path_remove
untrusted_set_sender = *
helo_allow_chars = _
daemon_smtp_ports = 25 : 109 : 587
bounce_message_file = /usr/local/etc/exim/bounce_message_file
warn_message_file = /usr/local/etc/exim/warn_message_file
return_size_limit = 10000
bounce_return_message = true
bounce_return_size_limit = 1000
delay_warning = 72h
smtp_accept_max = 100
smtp_accept_max_per_host = 10
smtp_return_error_details = yes
log_selector = +incoming_interface +deliver_time +delivery_size
+received_sender \
+received_recipients +sender_on_delivery +subject +address_rewrite
+all_parents
# log_selector = +all
message_logs = false
#
# My Attempt at greylisting
#
hide mysql_servers = localhost/exim_db/<exim_db>/<passwd>:
GREYLIST_TEST = SELECT IF(NOW() > block_expires, 2, 1) \
FROM exim_greylist \
WHERE relay_ip = '${quote_mysql:$sender_host_address}' \
AND from_domain = '${quote_mysql:$sender_address_domain}' \
AND record_expires > NOW()
GREYLIST_ADD = INSERT INTO exim_greylist \
SET relay_ip = '${quote_mysql:$sender_host_address}', \
from_domain = '${quote_mysql:$sender_address_domain}', \
block_expires = DATE_ADD(NOW(), INTERVAL 1 MINUTE), \
record_expires = DATE_ADD(NOW(), INTERVAL 14 DAY), \
origin_type = 'AUTO', \
create_time = NOW()
GREYLIST_UPDATE = UPDATE exim_greylist \
SET record_expires = DATE_ADD(now(), INTERVAL 14 DAY) \
WHERE relay_ip = '${quote_mysql:$sender_host_address}' \
AND from_domain = '${quote_mysql:$sender_address_domain}' \
AND record_expires > NOW()
######################################################################
# ACL CONFIGURATION #
# Specifies access control lists for incoming SMTP mail #
######################################################################
begin acl
acl_check_rcpt:
accept hosts = :
logwrite = ACL - ACCEPTED (EMPTY LIST)
deny local_parts = ^.*[@%!/|] : ^\\.
log_message = ACL - DENIED (LOCAL PART SYNTAX)
accept authenticated = *
logwrite = ACL - ACCEPTED (AUTHENTICATED)
endpass
accept hosts = +relay_from_hosts
logwrite = ACL - ACCEPTED (RELAY FROM HOST LIST)
endpass
######################################################################
# Hello checks added November 1 2009.
######################################################################
# If the remote host greets with an IP address, then reject the mail.
deny message = RATWARE - IP address.
log_message = ACL - DENIED - RATWARE remote host used IP
address \
in HELO/EHLOgreeting
condition = ${if isip
{$sender_helo_name}{true}{false}}
# Likewise if the peer greets with one of our own names
deny message = RATWARE - Fake HELO Domain
log_message = ACL - DENIED - RATWARE remote host used
our name in \
HELO/EHLO greeting.
condition = ${if match_domain{$sender_helo_name}\
{$primary_hostname:+local_domains:+relay_to_domains}\
{true}{false}}
deny message = RATWARE - No HELO
log_message = ACL - DENIED - RATWARE remote host did not
present \
HELO/EHLO greeting.
condition = ${if def:sender_helo_name {false}{true}}
# If HELO verification fails, we add a X-HELO-Warning: header in the
message.
warn message = X-HELO-Warning: Remote host
$sender_host_address \
${if def:sender_host_name
{($sender_host_name) }}\
incorrectly presented itself as
$sender_helo_name
log_message = ACL - WARN - UNVERIFIABLE HELO/EHLO
greeting.
!verify = helo
#######################################################################
# Mail is being rejected on some hosts because the mail MX is only set to
Reflexion
# and our server is rejecting it because some mail servers see the lesser
priorty
# MX and try to oour server directly instead of going though Reflexion.
# UPDATE: All secondary MXs removed from DNS zones. Reenabled monday Oct 5
2009.
accept domains = +filtered_domains
hosts = +filtering_hosts
verify = recipient
log_message = ACL - ACCEPTED - MXTEXT
deny message = Please use the public MX server for the
domain $domain
domains = +filtered_domains
hosts = !+filtering_hosts
log_message = ACL - DENIED - MXTEST
######################################################################
######################################################################
# DNS checks
######################################################################
# The results of these checks are cached, so multiple recipients
# does not translate into multiple DNS lookups.
#
# If the connecting host is in one of a select few DNSbls, then
# reject the message. Be careful when selecting these lists; many
# would cause a large number of false postives, and/or have no
# clear removal policy.
#
# deny dnslists = dnsbl.sorbs.net : \
# dnsbl.njabl.org : \
# cbl.abuseat.org : \
# bl.spamcop.net
# message = RBL - $sender_host_address is listed in
$dnslist_domain\
# ${if def:dnslist_text { ($dnslist_text)}}
#####################################################################
deny senders = :
condition = ${if > {$recipients_count}{2}{1}}
message = Bounces must have only a single recipient
log_message = ACL - DENIED - BACKSCATTER - RECIPIENTS
$recipients_count
deny message = rejected because $sender_host_address was
\
found in our blacklist
hosts = +blacklisted_domains
log_message = ACL - DENIED - BLACKLISTED DOMAIN FOUND IN
$blacklisted_domains
deny
! condition = ${lookup
dnsdb{defer_never,ptr=$sender_host_address}{yes}}
log_message = ACL - DENIED - NO PTR [rDNS] FOUND FOR
$sender_host_address
message = We do not accept mail from hosts with
missing \
or incorrect rDNS.
deny senders = :
! hosts = +whitelist
! domains = +local_domains
dnslists = ips.backscatterer.org
message = This message looks like a bounce, and your
server is listed at \
ips.backscatterer.org, so I assume that this
is "backscatter". \
Please configure your mail server to not
send "backscatter \ spam". \
For advice, try
http://www.dontbouncespam.org/
log_message = ACL - DENIED - BACKSCATTER - INCOMING
warn set acl_m2 = ${lookup mysql{GREYLIST_TEST}{$value}{0}}
defer ! hosts = +whitelist
! hosts = +relay_from_hosts
! authenticated = *
condition = ${if eq{$acl_m2}{0}{yes}}
condition = ${lookup mysql{GREYLIST_ADD}{yes}{no}}
message = Now greylisted - please try again in 1
minute.
log_message = ACL - DEFERED - ADDING TO GREYLIST
defer ! hosts = +whitelist
! hosts = +relay_from_hosts
! authenticated = *
condition = ${if eq{$acl_m2}{1}{yes}}
message = Still greylisted - please try again in 1
minute.
log_message = ACL - DEFERED - STILL GREYLISTED
defer
! hosts = +whitelist
! hosts = +relay_from_hosts
! authenticated = *
condition = ${lookup mysql{GREYLIST_UPDATE}{no}{no}}
message = Greylist update failed
log_message = ACL - DEFERED - GREYLIST UPDATE FAILED
require verify = sender
accept hosts = +spf_bypass
spf = fail
logwrite = SPF - REFLEXION $sender_host_address is OK
for \
$sender_address_domain
deny message = SPF - INCOMING $sender_host_address \
is not allowed to send mail from
$sender_address_domain
spf = fail
log_message = ACL - DENIED - SPF Mismatch
accept domains = +local_domains
endpass
message = unknown user
verify = recipient
accept domains = +relay_to_domains
endpass
message = unrouteable address
verify = recipient
######################################################################
# ROUTERS CONFIGURATION #
# Specifies how addresses are handled #
######################################################################
# THE ORDER IN WHICH THE ROUTERS ARE DEFINED IS IMPORTANT! #
# An address is passed to each router in turn until it is accepted. #
######################################################################
begin routers
dnslookup_owm_www:
driver = dnslookup
domains = ! +local_domains
condition = ${if eq {$sender_host_address}{127.0.0.1} {yes}{no}}
transport = remote_smtp
ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
no_more
dnslookup_local:
driver = dnslookup
domains = ! +local_domains
condition = ${lookup {$sender_address_domain} lsearch
{/etc/virtual/domains} {yes}{no}}
transport = remote_smtp
ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
no_more
dnslookup_bounce:
driver = dnslookup
domains = ! +local_domains
condition = ${if eq {$sender_address_local_part}{} {yes}{no}}
transport = remote_smtp
ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
no_more
dnslookup_alias:
driver = dnslookup
domains = ! +local_domains
transport = remote_smtp
ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
no_more
spamcheck_router:
driver = accept
no_verify
condition = "${if and { {!def:h_X-Spam-Flag:} {!eq {$received_protocol}\
{spam-scanned}}} {1}{0}}"
transport = spamcheck
virtual_alias:
driver = redirect
allow_defer
allow_fail
data = ${lookup {$local_part} lsearch {/home/$domain/mail/aliases}}
domains = /etc/virtual/domains
require_files = /home/$domain/mail/aliases
condition = ${lookup {$local_part} lsearch {/home/$domain/mail/aliases}
{yes}{no}}
qualify_preserve_domain
retry_use_local_part
check_ancestor
one_time
file_transport = address_file
pipe_transport = address_pipe
reply_transport = address_reply
autoreply_router:
driver = accept
require_files = /home/$domain/mail/auto-replies/$local_part
transport = autoreply_transport
no_verify
unseen
virtual_localuser:
driver = accept
require_files = /etc/virtual/$domain/passwd
domains = /etc/virtual/domains
condition = ${lookup {$local_part} lsearch
{/etc/virtual/$domain/passwd}{$value}}
transport = virtual_localdelivery
virtual_catchall:
driver = redirect
allow_defer
allow_fail
data = ${lookup {catchall} lsearch {/home/$domain/mail/aliases}}
domains = /etc/virtual/domains
require_files = /home/$domain/mail/aliases
condition = ${lookup {catchall}lsearch{/home/$domain/mail/aliases}
{yes}{no}}
qualify_preserve_domain
retry_use_local_part
check_ancestor
one_time
file_transport = address_file
pipe_transport = address_pipe
reply_transport = address_reply
localuser:
driver = accept
check_local_user
condition = ${lookup {$sender_helo_name} lsearch
{/etc/virtual/domains}{YES}{NO}}
transport = local_delivery
######################################################################
# TRANSPORTS CONFIGURATION #
######################################################################
# ORDER DOES NOT MATTER #
# Only one appropriate transport is called for each delivery. #
######################################################################
begin transports
remote_smtp:
driver = smtp
return_path_add = true
autoreply_transport:
driver = pipe
command = /usr/local/bin/autoreply.pl
/home/$domain/mail/auto-replies/$local_part
spamcheck:
driver = pipe
command = /usr/local/sbin/exim -oMr spam-scanned -bS
use_bsmtp = true
transport_filter = /usr/local/bin/spamc -u
${lookup{$domain}lsearch{/etc/virtual/domains_users}}
home_directory = "/tmp"
current_directory = "/tmp"
# must use a privileged user to set $received_protocol on the way back in!
user = mailnull
group = mailnull
log_output = true
return_fail_output = false
return_path_add
message_prefix =
message_suffix =
virtual_localdelivery:
driver = appendfile
create_directory = true
directory_mode = 700
file = /var/spool/virtual/${domain}/${local_part}
headers_remove = "Bcc"
return_path_add
user = ${lookup{$domain}lsearch{/etc/virtual/domains_users}}
group = mail
mode = 660
local_delivery:
driver = appendfile
file = /$home/mail/$local_part
delivery_date_add
envelope_to_add
return_path_add
user = mailnull
group = mail
mode = 0660
address_pipe:
driver = pipe
return_output
user = <user>
address_file:
driver = appendfile
delivery_date_add
envelope_to_add
return_path_add
address_reply:
driver = autoreply
######################################################################
# RETRY CONFIGURATION #
######################################################################
begin retry
# Domain Error Retries
# ------ ----- -------
* quota_7d
* quota F,72h,1h;
* * F,30m,1m; F,90m,5m; F,22h,30m; F,144h,60m
######################################################################
# REWRITE CONFIGURATION #
######################################################################
# There are no rewriting specifications in this default configuration file.
begin rewrite
######################################################################
# AUTHENTICATION CONFIGURATION #
######################################################################
# There are no authenticator specifications in this default configuration
file.
begin authenticators
# For Netscape/Mozilla
plain:
driver = plaintext
public_name = PLAIN
server_condition = "${if and{ {!eq{$2}{}}{!eq{$3}{}} \
{crypteq {$3} {${lookup {${local_part:$2}} lsearch \
{/etc/virtual/${domain:$2}/passwd}\
{$value} {*:*}}}} } {1}{0}}"
server_set_id = $2
# For Outlook/Outlook Express
login:
driver = plaintext
public_name = LOGIN
server_prompts = "Username:: : Password::"
server_condition = "${if and{ {!eq{$1}{}}{!eq{$2}{}} \
{crypteq {$2} {${lookup {${local_part:$1}} lsearch \
{/etc/virtual/${domain:$1}/passwd}\
{$value} {*:*}}}} } {1}{0}}"
server_set_id = $1
# End of Exim configuration file
