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Old 26th April 2009, 15:36
bob808 bob808 is offline
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Default My postfix server is beeing used to send large ammounts of spam.

Hello people. I have a big problem. My postfix server is beeing used to send large ammounts of spam. I noticed this a few days ago when users from my network were complaining that some of their email end up as spam in other networks. I configured my mail server properly and dns also, and that usually didn't happen. Last night one user forwarded me an email from gmail:

The mail system

<example@gmail.com>: delivery temporarily suspended: host
alt4.gmail-smtp-in.l.google.com[209.85.221.90] refused to talk to me:
421-4.7.0 [89.xxx.yyy.zzz] Our system has detected an unusual amount of
421-4.7.0 unsolicited mail originating from your IP address. To protect
our
421-4.7.0 users from spam, mail sent from your IP address has been
temporarily 421-4.7.0 blocked. Please visit
http://www.google.com/mail/help/bulk_mail.html 421 4.7.0 to review our
Bulk
Email Senders Guidelines. 30si2121724qyk.13


and I started to worry . My build is made exactly like this http://www.howtoforge.com/perfect-server-ubuntu-8.10 . I checked the server, and the mailqueue was 10.000 long. That's nuts for a company with 30 total mail users, by witch 10 are very active. So I started to dig arround... (elementary my dear Watson ) ) and then I saw the logs. At least I tried to but „cat” and „less” were going nuts..so I downloaded the logs so I can check them proper from a decent graphical text editor. Because they were 150 megs long for a day last 3-4 days. Time to check out what's going on. Couldn't understand jack since I am relatively new to linux world. The large amount of data in the logs was the thing that really worried me. After a few test mails, I realized that Gmail and Yahoo are refusing the mails coming from my server. Internal emails were slowed alot last days, and alot of incoming mail was marked as spam, even from trusted domains we used for exchanging data.
First actions I took the action of blocking port 25 by witch mail servers cumunicate to each other. Commented out the following line from /etc/postfix/master.cf :

smtp inet n - - - - smtpd

restarted then shut down postfix and then I cleaned the postfix queue with „postsuper -d ALL”, finalising with killing each process that was in the list of „lsof -i :25” (like 40-50 entries). Now postfix doesn't send out spam. Emails inside the network work very good now, we can send out emails, we just can't receive any outside email since I closed port 25. What can I do next to receive emails from outside, minus the spam problem?

Here are the config files and logs:
/etc/postfix/main.cf :

# See /usr/share/postfix/main.cf.dist for a commented, more complete version


# Debian specific: Specifying a file name will cause the first
# line of that file to be used as the name. The Debian default
# is /etc/mailname.
#myorigin = /etc/mailname

smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu)
biff = no

# appending .domain is the MUA's job.
append_dot_mydomain = no

# Uncomment the next line to generate "delayed mail" warnings
delay_warning_time = 4h
unknown_local_recipient_reject_code = 450
maximal_queue_lifetime = 7d
minimal_backoff_time = 1000s
maximal_backoff_time = 8000s
readme_directory = no

# TLS parameters
smtpd_tls_cert_file = /etc/postfix/ssl/smtpd.crt
smtpd_tls_key_file = /etc/postfix/ssl/smtpd.key
smtpd_use_tls = yes
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache
#smtpd_tls_ask_ccert = yes
#smtpd_tls_req_ccert = no
smtp_tls_cert_file = /etc/postfix/ssl/smtp.crt
smtp_tls_key_file = /etc/postfix/ssl/smtp.key
smtp_tls_CAfile = /etc/postfix/ssl/cacertt.pem

# See /usr/share/doc/postfix/TLS_README.gz in the postfix-doc package for
# information on enabling SSL in the smtp client.

mydomain = mydomain.com
myhostname = mail.mydomain.com
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
myorigin = /etc/mailname
mydestination = /etc/postfix/local-host-names
relayhost =
mynetworks = 89.xxx.yyy.0/30, 127.0.0.0/8
mailbox_command = procmail -a "$EXTENSION"
mailbox_size_limit = 0
message_size_limit = 50000000
recipient_delimiter = +
inet_interfaces = all
inet_protocols = ipv4
smtpd_sasl_local_domain =
smtpd_sasl_auth_enable = yes
smtpd_sasl_security_options = noanonymous
broken_sasl_auth_clients = yes
smtpd_sasl_authenticated_header = yes
smtpd_recipient_restrictions = permit_sasl_authenticated,permit_mynetworks,reject _unauth_destination, reject_unauth_pipelining, reject_non_fqdn_recipient, reject_unknown_recipient_domain, reject_unauth_destination, permit
#smtpd_data_restrictions = reject_unauth_pipelining
#smtpd_helo_restrictions = permit_mynetworks, warn_if_reject reject_non_fqdn_hostname, reject_invalid_hostname, permit
#smtpd_sender_restrictions = permit_mynetworks, warn_if_reject reject_non_fqdn_sender, reject_unknown_sender_domain, reject_unauth_pipelining, permit
#smtpd_client_restrictions = reject_rbl_client sbl.spamhaus.org, reject_rbl_client blackholes.easynet.nl, reject_rbl_client dnsbl.njabl.org
smtpd_helo_required = yes
smtpd_delay_reject = yes
disable_vrfy_command = yes
smtpd_recipient_limit = 100
smtpd_soft_error_limit = 10
smtpd_hard_error_limit = 20
smtpd_tls_auth_only = no
smtp_use_tls = yes
smtp_tls_note_starttls_offer = yes
smtpd_tls_CAfile = /etc/postfix/ssl/cacert.pem
smtpd_tls_loglevel = 2
smtpd_tls_received_header = yes
smtpd_tls_session_cache_timeout = 3600s
tls_random_source = dev:/dev/urandom
message_size_limit = 52400000
virtual_maps = hash:/etc/postfix/virtusertable


and /etc/postfix/master.cf

#
# Postfix master process configuration file. For details on the format
# of the file, see the master(5) manual page (command: "man 5 master").
#
# Do not forget to execute "postfix reload" after editing this file.
#
# ================================================== ========================
# service type private unpriv chroot wakeup maxproc command + args
# (yes) (yes) (yes) (never) (100)
# ================================================== ========================
#smtp inet n - - - - smtpd
-o message_size_limit=50000000
submission inet n - - - - smtpd
smtps inet n - - - - smtpd
-o smtpd_tls_security_level=encrypt
-o smtpd_sasl_auth_enable=yes
-o smtpd_client_restrictions=permit_sasl_authenticate d,reject
-o milter_macro_daemon_name=ORIGINATING
-o smtpd_tls_wrappermode=yes
-o message_size_limit=25000000
#628 inet n - - - - qmqpd
pickup fifo n - - 60 1 pickup
cleanup unix n - - - 0 cleanup
qmgr fifo n - n 300 1 qmgr
#qmgr fifo n - - 300 1 oqmgr
tlsmgr unix - - - 1000? 1 tlsmgr
rewrite unix - - - - - trivial-rewrite
bounce unix - - - - 0 bounce
defer unix - - - - 0 bounce
trace unix - - - - 0 bounce
verify unix - - - - 1 verify
flush unix n - - 1000? 0 flush
proxymap unix - - n - - proxymap
proxywrite unix - - n - 1 proxymap
smtp unix - - - - - smtp
# When relaying mail as backup MX, disable fallback_relay to avoid MX loops
relay unix - - - - - smtp
-o smtp_fallback_relay=
# -o smtp_helo_timeout=5 -o smtp_connect_timeout=5
showq unix n - - - - showq
error unix - - - - - error
retry unix - - - - - error
discard unix - - - - - discard
local unix - n n - - local
virtual unix - n n - - virtual
lmtp unix - - - - - lmtp
anvil unix - - - - 1 anvil
scache unix - - - - 1 scache
#
# ================================================== ==================
# Interfaces to non-Postfix software. Be sure to examine the manual
# pages of the non-Postfix software to find out what options it wants.
#
# Many of the following services use the Postfix pipe( delivery
# agent. See the pipe( man page for information about ${recipient}
# and other message envelope options.
# ================================================== ==================
#
# maildrop. See the Postfix MAILDROP_README file for details.
# Also specify in main.cf: maildrop_destination_recipient_limit=1
#
maildrop unix - n n - - pipe
flags=DRhu user=vmail argv=/usr/bin/maildrop -d ${recipient}
#
# See the Postfix UUCP_README file for configuration details.
#
uucp unix - n n - - pipe
flags=Fqhu user=uucp argv=uux -r -n -z -a$sender - $nexthop!rmail ($recipient)
#
# Other external delivery methods.
#
ifmail unix - n n - - pipe
flags=F user=ftn argv=/usr/lib/ifmail/ifmail -r $nexthop ($recipient)
bsmtp unix - n n - - pipe
flags=Fq. user=bsmtp argv=/usr/lib/bsmtp/bsmtp -t$nexthop -f$sender $recipient
scalemail-backend unix - n n - 2 pipe
flags=R user=scalemail argv=/usr/lib/scalemail/bin/scalemail-store ${nexthop} ${user} ${extension}
mailman unix - n n - - pipe
flags=FR user=list argv=/usr/lib/mailman/bin/postfix-to-mailman.py
${nexthop} ${user}


/var/log/mail.info (a small part)

Apr 25 07:09:07 server1 postfix/smtp[24538]: connect to mhost01h.leeds.ac.uk[129.11.77.238]:25: Connection timed out
Apr 25 07:09:07 server1 postfix/smtp[24554]: connect to video.fox23news.com[66.179.120.80]:25: Connection timed out
Apr 25 07:09:07 server1 postfix/smtp[24554]: C3B3959462A: to=<82817@video.fox23news.com>, relay=none, delay=474297, delays=474267/0.15/30/0, dsn=4.4.1, status=deferred (connect to video.fox23news.com[66.179.120.80]:25: Connection timed out)
Apr 25 07:09:07 server1 postfix/smtp[24554]: C3B3959462A: to=<82849@video.fox23news.com>, relay=none, delay=474297, delays=474267/0.15/30/0, dsn=4.4.1, status=deferred (connect to video.fox23news.com[66.179.120.80]:25: Connection timed out)
Apr 25 07:09:07 server1 postfix/smtp[24554]: C3B3959462A: to=<82862@video.fox23news.com>, relay=none, delay=474297, delays=474267/0.15/30/0, dsn=4.4.1, status=deferred (connect to video.fox23news.com[66.179.120.80]:25: Connection timed out)
Apr 25 07:09:07 server1 postfix/smtp[24554]: C3B3959462A: to=<82867@video.fox23news.com>, relay=none, delay=474297, delays=474267/0.15/30/0, dsn=4.4.1, status=deferred (connect to video.fox23news.com[66.179.120.80]:25: Connection timed out)
Apr 25 07:09:07 server1 postfix/smtp[24554]: C3B3959462A: to=<82868@video.fox23news.com>, relay=none, delay=474297, delays=474267/0.15/30/0, dsn=4.4.1, status=deferred (connect to video.fox23news.com[66.179.120.80]:25: Connection timed out)
Apr 25 07:09:07 server1 postfix/smtp[24554]: C3B3959462A: to=<82869@video.fox23news.com>, relay=none, delay=474297, delays=474267/0.15/30/0, dsn=4.4.1, status=deferred (connect to video.fox23news.com[66.179.120.80]:2


/var/log/mail.warn


pr 25 16:27:19 server1 last message repeated 2 times
Apr 25 16:27:19 server1 postfix/smtp[6947]: warning: open active 52500595847: No such file or directory
Apr 25 16:27:19 server1 postfix/smtp[6947]: warning: open active 3B2B25949CA: No such file or directory
Apr 25 16:27:19 server1 postfix/smtp[6947]: warning: open active 63927595257: No such file or directory
Apr 25 16:27:19 server1 postfix/smtp[6947]: warning: open active 6D766595A09: No such file or directory
Apr 25 16:27:19 server1 postfix/smtp[6947]: warning: open active E4E14594BC2: No such file or directory
Apr 25 16:27:19 server1 postfix/smtp[6947]: warning: open active 4208A594956: No such file or directory
Apr 25 16:27:19 server1 postfix/smtp[6947]: warning: open active 3F288594FFF: No such file or directory
Apr 25 16:27:19 server1 postfix/smtp[6947]: warning: open active 163331D4A89: No such file or directory
Apr 25 16:27:19 server1 postfix/smtp[6947]: warning: open active E9D721D1BD3: No such file or directory
Apr 25 16:27:19 server1 postfix/smtp[6947]: warning: open active 7C2A91D0C66: No such file or directory
Apr 25 16:27:19 server1 postfix/smtp[6947]: warning: open active 4A67C5948A7: No such file or directory
Apr 25 16:27:19 server1 postfix/smtp[6947]: warning: open active 4A67C5948A7: No such file or directory
Apr 25 16:27:19 server1 postfix/smtp[6947]: warning: open active AF9681D1B30: No such file or directory
Apr 25 16:27:19 server1 postfix/smtp[6947]: warning: open active 3AE40595C6D: No such file or directory
Apr 25 16:27:19 server1 postfix/smtp[6947]: warning: open active BDDEF1D1879: No such file or directory
Apr 25 16:27:19 server1 postfix/smtp[6947]: warning: open active BDDEF1D1879: No such file or directory
Apr 25 16:27:19 server1 postfix/smtp[6947]: warning: open active A203C1D1A8B: No such file or directory
Apr 25 16:27:19 server1 postfix/smtp[6947]: warning: open active BAA47595EC0: No such file or directory
Apr 25 16:27:19 server1 postfix/smtp[6947]: warning: open active 38F311D100F: No such file or directory


/var/log/mail.log


Apr 25 07:08:37 server1 postfix/qmgr[17815]: 1D2A41D4775: from=<E-cards@Hallmark.com>, size=2084, nrcpt=16 (queue active)
Apr 25 07:08:37 server1 postfix/qmgr[17815]: 182C51D474A: from=<E-cards@Hallmark.com>, size=2084, nrcpt=16 (queue active)
Apr 25 07:08:37 server1 postfix/qmgr[17815]: 1FEAF1D194E: from=<E-cards@Hallmark.com>, size=2190, nrcpt=16 (queue active)
Apr 25 07:08:37 server1 postfix/qmgr[17815]: 120B11D1AF7: from=<E-cards@Hallmark.com>, size=2190, nrcpt=16 (queue active)
Apr 25 07:08:37 server1 postfix/qmgr[17815]: 138CE594CCF: from=<E-cards@Hallmark.com>, size=2147, nrcpt=16 (queue active)
Apr 25 07:08:37 server1 postfix/qmgr[17815]: 1FB985959B7: from=<E-cards@Hallmark.com>, size=2181, nrcpt=16 (queue active)
Apr 25 07:08:37 server1 postfix/qmgr[17815]: 179EC5943A2: from=<E-cards@Hallmark.com>, size=2147, nrcpt=16 (queue active)
Apr 25 07:08:37 server1 postfix/qmgr[17815]: 196335945FE: from=<E-cards@Hallmark.com>, size=2147, nrcpt=16 (queue active)
Apr 25 07:08:37 server1 postfix/qmgr[17815]: 163401D187D: from=<E-cards@Hallmark.com>, size=2190, nrcpt=16 (queue active)
Apr 25 07:08:37 server1 postfix/qmgr[17815]: 157D31D144A: from=<E-cards@Hallmark.com>, size=2190, nrcpt=16 (queue active)
Apr 25 07:08:37 server1 postfix/qmgr[17815]: 14113595D24: from=<E-cards@Hallmark.com>, size=2190, nrcpt=16 (queue active)
Apr 25 07:08:37 server1 postfix/qmgr[17815]: 1868F1D15A8: from=<E-cards@Hallmark.com>, size=2190, nrcpt=16 (queue active)
Apr 25 07:08:37 server1 postfix/qmgr[17815]: 15E0C1D4841: from=<E-cards@Hallmark.com>, size=2084, nrcpt=16 (queue active)
Apr 25 07:08:37 server1 postfix/qmgr[17815]: 142E31D4D5D: from=<E-cards@Hallmark.com>, size=2084, nrcpt=16 (queue active)
Apr 25 07:08:37 server1 postfix/qmgr[17815]: 12159595887: from=<E-cards@Hallmark.com>, size=2181, nrcpt=16 (queue active)
Apr 25 07:08:37 server1 postfix/error[24557]: 126F21D140C: to=<billingcompliance@ouhsc.edu>, relay=none, delay=165993, delays=165993/0.04/0/0.06, dsn=4.0.0, status=deferred (delivery temporarily suspended: host smtp4.ouhsc.edu[157.142.11.65] refused to talk to me: 554 smtp4 ESMTP Blocked - see https://support.proofpoint.com/dnsbl...89.238.221.142)
Apr 25 07:08:37 server1 postfix/error[24536]: 1FEAF1D194E: to=<rbrevett@lincoln.edu>, relay=none, delay=163665, delays=163665/0/0/0.06, dsn=4.0.0, status=deferred (delivery temporarily suspended: host smtp3.lincoln.edu[192.131.155.110] refused to talk to me: 554 pps1.lincoln.edu ESMTP not accepting messages)
Apr 25 07:08:37 server1 postfix/error[24559]: 1482E1D12AE: to=<astrid-rasmussen@ouhsc.edu>, relay=none, delay=166105, delays=166105/0.04/0/0.08, dsn=4.0.0, status=deferred (delivery temporarily suspended: host smtp4.ouhsc.edu[157.142.11.65] refused to talk to me: 554 smtp4 ESMTP Blocked - see https://support.proofpoint.com/dnsbl...89.238.221.142)
Apr 25 07:08:37 server1 postfix/error[24535]: 1D2A41D4775: to=<geoshorty@home.com>, relay=none, delay=26981, delays=26981/0.04/0/0.08, dsn=4.4.1, status=deferred (delivery temporarily suspended: connect to mx1.home.com[10.42.23.11]:25: Connection timed out)
Apr 25 07:08:37 server1 postfix/error[24566]: 1868F1D15A8: to=<tj_sutton@bellsouth.net>, relay=none, delay=230975, delays=230975/0.02/0/0.03, dsn=4.0.0, status=deferred (delivery temporarily suspended: host gateway-f1.isp.att.net[204.127.217.16] refused to talk to me: 550-89.238.221.142 blocked by ldapu=rblmx,dc=att,dc=net 550 Error - Blocked for abuse. See http://att.net/blocks)
Apr 25 07:08:37 server1 postfix/error[24565]: 120B11D1AF7: to=<rdaerr@kent.edu>, relay=none, delay=163652, delays=163652/0.03/0/0.03, dsn=4.0.0, status=deferred (delivery temporarily suspended: host mx2.kent.edu.gslb.pphosted.com[208.86.201.10] refused to talk to me: 554 mx.kent.edu.pph5a.pphosted.com ESMTP Blocked - see https://support.proofpoint.com/dnsbl...89.238.221.142)
Apr 25 07:08:37 server1 postfix/error[24566]: 1868F1D15A8: to=<tjacks78@bellsouth.net>, relay=none, delay=230975, delays=230975/0.02/0/0.05, dsn=4.0.0, status=deferred (delivery temporarily suspended: host gateway-f1.isp.att.net[204.127.217.16] refused to talk to me: 550-89.238.221.142 blocked by ldapu=rblmx,dc=att,dc=net 550 Error - Blocked for abuse. See http://att.net/blocks)
Apr 25 07:08:37 server1 postfix/qmgr[17815]: 186EB1D4366: from=<E-cards@Hallmark.com>, size=2105, nrcpt=16 (queue active)
Apr 25 07:08:37 server1 postfix/qmgr[17815]: 45CA11D1385: from=<E-cards@Hallmark.com>, size=2190, nrcpt=16 (queue active)
Apr 25 07:08:37 server1 postfix/qmgr[17815]: 4961259450F: from=<E-cards@Hallmark.com>, size=2147, nrcpt=16 (queue active)
Apr 25 07:08:37 server1 postfix/qmgr[17815]: 4F6151D10E1: from=<E-cards@Hallmark.com>, size=2190, nrcpt=16 (queue active)
Apr 25 07:08:37 server1 postfix/qmgr[17815]: 40D38594671: from=<E-cards@Hallmark.com>, size=2147, nrcpt=16 (queue active)
Apr 25 07:08:37 server1 postfix/qmgr[17815]: 46FC71D1362: from=<E-cards@Hallmark.com>, size=2190, nrcpt=16 (queue active)
Apr 25 07:08:37 server1 postfix/qmgr[17815]: 4EA371D1B18: from=<E-cards@Hallmark.com>, size=2190, nrcpt=16 (queue active)
Apr 25 07:08:37 server1 postfix/qmgr[17815]: 41F3B1D4B20: from=<E-cards@Hallmark.com>, size=2084, nrcpt=16 (queue active)
Apr 25 07:08:37 server1 postfix/qmgr[17815]: 440D51D152A: from=<E-cards@Hallmark.com>, size=2190, nrcpt=16 (queue active)


What can I do?

Thank you very much for reading my problem, and have a nice evening.
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  #2  
Old 27th April 2009, 12:29
dipeshmehta dipeshmehta is offline
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Default

Hello,

I faced similar problem at one of my client's setup.

These mails must be originated from only one or two ids on your server, most probably with generic username/passwd like admin/admin, store/store, administrator/admin etc. You may check mail logs, mail queue etc., and check auth.log also.

After getting the username, check that user's home directory... you may find some malicious scripts and unusual directories into the same. Remove them, or if you are not sure about any directory, you can move them to some another place, where no one has access.

Change passwd for that user, remove mails from differed queue, & you're done.

Hope this helps.

Dipesh
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  #3  
Old 27th April 2009, 12:37
rdv25772 rdv25772 is offline
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Default mail relay????

It looks to me that you have a mail relay server.

Please try http://www.abuse.net/relay.html to find out if any test on this site will pass. If so, you have a problem.

I hope this will help a bit.
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