Re: Mail forwarding loop

Thu, 08 Nov 2012 14:11:38 -0800 

On 11/08/2012 05:25 PM, Daniele Nicolodi wrote:

Hello,

I think I have a problem with my simple mail server. I noticed several
bounce mails in the queue, which postfix in unable to deliver.


C0B0160EC     12730 Thu Nov  8 12:35:47  MAILER-DAEMON
(lost connection with eforward5.registrar-servers.com[38.101.213.202] while 
receiving the initial server greeting)
                                          instant.checkm...@designakeackson.info

All of them destined to what look to be fake addresses. The original
mails that originate the bounce are indeed spam.

On this server I use spamassassin as content filter, which re-injects
the mail into postfix after scanning it via local delivery. Spam is then
discarded via a sieve rule (not bounced).

It looks like postfix detects a mail forwarding loop when the mail is
re-injected by spamassassin via local delivery. Why isn't the loop
detected when the mail is received by the smtpd?


Postfix cannot detect a mail loop if it has never seen the message before.
You are not re-injecting the filtered message, you are calling sendmail(1), which in turn invokes pickup(8): 


  I do not like to
generate unnecessary bounce mails. Is this a real problem? How can I fix it?

Here is what I think is a relevant log excerpt:


# egrep 2ABF060A6\|BCDF560EF\|C0B0160EC\|FD01D4DD-1DEF-1BC3-9A2A-5EDE8F9DD6C5 
/var/log/mail.log
Nov  8 12:35:46 zed postfix/smtpd[2515]: 2ABF060A6: 
client=designakeackson.info[176.126.174.9]
Nov  8 12:35:46 zed postfix/cleanup[2517]: 2ABF060A6: 
message-id=<fd01d4dd-1def-1bc3-9a2a-5ede8f9dd...@designakeackson.info>
Nov  8 12:35:46 zed postfix/qmgr[3850]: 2ABF060A6: 
from=<instant.checkm...@designakeackson.info>, size=9793, nrcpt=1 (queue active)
Nov  8 12:35:46 zed spamd[2282]: spamd: processing message 
<fd01d4dd-1def-1bc3-9a2a-5ede8f9dd...@designakeackson.info> for daniele:1000
Nov  8 12:35:47 zed spamd[2282]: spamd: result: Y 5 - 
BAYES_50,HTML_MESSAGE,RP_MATCHES_RCVD,SPF_SOFTFAIL,T_FILL_THIS_FORM_SHORT,URIBL_DBL_SPAM,URIBL_JP_SURBL,URIBL_WS_SURBL
 
scantime=1.4,size=9786,user=daniele,uid=1000,required_score=5.0,rhost=localhost,raddr=127.0.0.1,rport=60966,mid=<fd01d4dd-1def-1bc3-9a2a-5ede8f9dd...@designakeackson.info>,bayes=0.500000,autolearn=no
Nov  8 12:35:47 zed postfix/pickup[2485]: BCDF560EF: uid=65534 
from=<instant.checkm...@designakeackson.info>
Nov  8 12:35:47 zed postfix/cleanup[2517]: BCDF560EF: 
message-id=<fd01d4dd-1def-1bc3-9a2a-5ede8f9dd...@designakeackson.info>
Nov  8 12:35:47 zed postfix/pipe[2518]: 2ABF060A6: to=<dani...@grinta.net>, 
relay=spamassassin, delay=1.7, delays=0.24/0.01/0/1.4, dsn=2.0.0, status=sent 
(delivered via spamassassin service)
Nov  8 12:35:47 zed postfix/qmgr[3850]: BCDF560EF: 
from=<instant.checkm...@designakeackson.info>, size=10941, nrcpt=1 (queue 
active)
Nov  8 12:35:47 zed postfix/qmgr[3850]: 2ABF060A6: removed
Nov  8 12:35:47 zed postfix/local[2522]: BCDF560EF: to=<dani...@grinta.net>, 
relay=local, delay=0.02, delays=0/0.01/0/0.01, dsn=5.4.6, status=bounced (mail 
forwarding loop for dani...@grinta.net)
Nov  8 12:35:47 zed postfix/cleanup[2517]: C0B0160EC: 
message-id=<20121108123547.c0b016...@zed.grinta.net>
Nov  8 12:35:47 zed postfix/bounce[2523]: BCDF560EF: sender non-delivery 
notification: C0B0160EC
Nov  8 12:35:47 zed postfix/qmgr[3850]: C0B0160EC: from=<>, size=12730, nrcpt=1 
(queue active)
Nov  8 12:35:47 zed postfix/qmgr[3850]: BCDF560EF: removed
Nov  8 12:35:52 zed postfix/smtp[2512]: C0B0160EC: host 
eforward3.registrar-servers.com[209.105.246.196] said: 450 4.1.1 
<instant.checkm...@designakeackson.info>: Recipient address rejected: unverified address: 
unknown user: "instant.checkm...@designakeackson.info" (in reply to RCPT TO command)
Nov  8 12:35:52 zed postfix/smtp[2512]: C0B0160EC: host 
eforward1.registrar-servers.com[69.160.33.82] refused to talk to me: 421 4.3.2 
All server ports are busy
Nov  8 12:35:54 zed postfix/smtp[2512]: C0B0160EC: to=<instant.checkm...@designakeackson.info>, 
relay=eforward2.registrar-servers.com[209.105.246.195]:25, delay=7.2, delays=0/0/7/0.17, dsn=4.1.1, 
status=deferred (host eforward2.registrar-servers.com[209.105.246.195] said: 450 4.1.1 
<instant.checkm...@designakeackson.info>: Recipient address rejected: unverified address: 
unknown user: "instant.checkm...@designakeackson.info" (in reply to RCPT TO command))
Nov  8 12:45:42 zed postfix/qmgr[3850]: C0B0160EC: from=<>, size=12730, nrcpt=1 
(queue active)
Nov  8 12:45:43 zed postfix/smtp[2566]: C0B0160EC: host 
eforward3.registrar-servers.com[209.105.246.196] refused to talk to me: 421 
4.3.2 All server ports are busy
Nov  8 12:46:05 zed postfix/smtp[2566]: C0B0160EC: host 
eforward2.registrar-servers.com[209.105.246.195] said: 450 4.1.1 
<instant.checkm...@designakeackson.info>: Recipient address rejected: unverified address: 
unknown user: "instant.checkm...@designakeackson.info" (in reply to RCPT TO command)
Nov  8 12:46:06 zed postfix/smtp[2566]: C0B0160EC: host 
eforward1.registrar-servers.com[69.160.33.82] refused to talk to me: 421 4.3.2 
All server ports are busy
Nov  8 12:46:06 zed postfix/smtp[2566]: C0B0160EC: host 
eforward4.registrar-servers.com[69.160.33.74] refused to talk to me: 421 4.3.2 
All server ports are busy
Nov  8 12:46:06 zed postfix/smtp[2566]: C0B0160EC: 
to=<instant.checkm...@designakeackson.info>, 
relay=eforward5.registrar-servers.com[38.101.213.202]:25, delay=619, 
delays=595/0.04/24/0, dsn=4.3.2, status=deferred (host 
eforward5.registrar-servers.com[38.101.213.202] refused to talk to me: 421 4.3.2 All 
server ports are busy)

My configuration:

# postconf -n
alias_database = hash:/etc/aliases
alias_maps = hash:/etc/aliases
allow_min_user = no
append_dot_mydomain = no
biff = no
config_directory = /etc/postfix
disable_vrfy_command = yes
home_mailbox = Maildir/
inet_interfaces = all
inet_protocols = ipv4
mailbox_command = /usr/lib/dovecot/dovecot-lda -f "$SENDER" -a "$RECIPIENT"
mailbox_size_limit = 0
message_size_limit = 0
mydestination = grinta.net, zed, zed.grinta.net, localhost
myhostname = zed.grinta.net
mynetworks = 127.0.0.0/8
myorigin = /etc/mailname
owner_request_special = no
readme_directory = no
recipient_delimiter = +
relayhost =
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache
smtpd_banner = $myhostname ESMTP
smtpd_data_restrictions = reject_unauth_pipelining, permit
smtpd_delay_reject = yes
smtpd_helo_required = yes
smtpd_recipient_restrictions = permit_sasl_authenticated
reject_invalid_hostname reject_non_fqdn_hostname reject_non_fqdn_sender
reject_non_fqdn_recipient reject_unknown_sender_domain
reject_unknown_recipient_domain permit_mynetworks
reject_unauth_destination reject_rbl_client zen.spamhaus.org
reject_rbl_client bhnc.njabl.org reject_rbl_client dul.dnsbl.sorbs.net
permit
smtpd_sasl_auth_enable = yes
smtpd_sasl_authenticated_header = yes
smtpd_sasl_path = private/auth
smtpd_sasl_type = dovecot
smtpd_tls_auth_only = yes
smtpd_tls_cert_file = /etc/postfix/postfix.cert
smtpd_tls_key_file = /etc/postfix/postfix.key
smtpd_tls_security_level = may
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
unknown_local_recipient_reject_code = 550


Thanks in advance for your help.

Cheers,
Daniele




--
J.

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