From: Comfy Couch (comfycouchxyzhotmail.com)
Date: Wed Dec 01 2004 - 12:15:44 CST

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Hello, got the following issue that I'm hopeful someone can help me with.
Problem:

I run an MX Backup service for a variety of domains.

Essentially I add a customer domain ("customer.com") to my
relay_domains with RHS "OK". There is no other per-domain
customization like special transports or anything.

Recently I have been seeing the following in my logs:

90C925C4950 4240 Sun Nov 28 12:55:29 cheapdrugsdecapacity.com
(delivery temporarily suspended: mail for customer.com loops back to myself)
                                          sam_2ucustomer.com
                                          sht92customer.com
                                          sk8joelcustomer.com
                                          stahlfried_futtcustomer.com
                                          strothkacustomer.com

Theory:
My server used to be known as mxb1.biz.company.com, but I
disliked the "1" and so prefer to use "mxb.biz.company.com",
even though both A records still exist, and a bunch of customer
domains still refer to "mxb1" for now.
So Postfix receives the mail and normally just punts it along to the
primary server (the customer box). But if that customer box goes
down, then the Postfix servers try to send to the next hop - which
they don't realize is actually themselves.
ie. the next MX record is "mxb1.biz.company.com" but "myhostname" =
mxb.biz.company.com, so then they mail themselves and we get
that "mail loops back to me error" ? And after a bit of this,
Postfix qmgr marks that mail destined for that domain as down.

eg.
## Mail sent on to customer mailserver just fine...

Dec 1 10:32:14 myserver001 postfix/smtp[33557]: AEE755C4901:
to=<bobancustomer.com>, relay=mail.customer.com[NNN.NNN.NNN.NNN], delay
=6, status=sent (250 2.0.0 Message received OK)

## Mail not sent to customer mailserver (perhaps down?):

Dec 1 10:40:32 myserver001 postfix/smtp[33481]: 450D55C4901:
to=<zackcustomer.com>,
relay=mxb1.biz.company.com[MMM.MMM.MMM.MMM]
, delay=33, status=deferred (mail for customer.com loops
back to myself)

## Subsequently mail to that domain, marked undeliverable

Dec 1 10:40:32 myserver001 postfix/smtp[33481]: 450D55C4901:
to=<easycustomer.com>,
relay=mxb1.biz.company.com[MMM.MMM.MMM.MMM],
delay=33, status=deferred (mail for customer.com loops
back to myself)

Dec 1 10:44:55 myserver001 postfix/qmgr[14333]: 641FC5C4942:
to=<maxwellcustomer.com>, relay=none, delay=0, status=deferred (d
elivery temporarily suspended: mail for customer.com loops back to
myself)

Dec 1 10:46:24 myserver001 postfix/qmgr[14333]: B9B9A5C491B:
to=<markcustomer.com>, relay=none, delay=212, status=deferred
  (delivery temporarily suspended: mail for customer.com loops back to
myself)

How can I fix this up?
Thanks in advance for your suggestions.

# ---------------------------------
# Configuration Information
# ---------------------------------

Postfix Version: 2.1.5

postconf -n

alias_database = hash:${config_directory}/aliases
alias_maps = hash:${config_directory}/aliases
biff = no
body_checks = regexp:${config_directory}/BC-anti-virus.regexp,
regexp:${config_directory}/BC-anti-spam.regexp
body_checks_size_limit = 25000
bounce_queue_lifetime = 6h
command_directory = /opt/postfix/sbin
config_directory = /opt/postfix/etc
daemon_directory = /opt/postfix/libexec
debug_peer_level = 2
default_process_limit = 1000
header_checks =
     regexp:${config_directory}/HC-anti-virus.regexp,
     regexp:${config_directory}/HC-anti-spam.regexp
html_directory = no
mail_owner = postfix
mailbox_size_limit = 25600000
mailq_path = /opt/postfix/bin/mailq
manpage_directory = /opt/postfix/man
maximal_queue_lifetime = 5d
message_size_limit = 25600000
mime_header_checks =
     regexp:${config_directory}/MHC-anti-virus.regexp,
     regexp:${config_directory}/MHC-anti-spam.regexp
mydomain = company.com
myhostname = mxb.biz.company.com
mynetworks_style = host
myorigin = company.com
newaliases_path = /opt/postfix/bin/newaliases
parent_domain_matches_subdomains =
     debug_peer_list, fast_flush_domains, mynetworks,
     permit_mx_backup_networks, qmqpd_authorized_clients, relay_domains
queue_directory = /var/spool/postfix
readme_directory = /opt/postfix/etc/Readmes
relay_domains = hash:$config_directory/relay_domains
sample_directory = $config_directory/Samples
sendmail_path = /opt/postfix/sbin/sendmail
setgid_group = postdrop
smtp_data_done_timeout = 300s
smtp_helo_timeout = 100s
smtp_mail_timeout = 500s
smtp_quit_timeout = 100s
smtp_rcpt_timeout = 100s
smtpd_authorized_xclient_hosts = localhost
smtpd_banner = $myhostname ESMTP
smtpd_delay_reject = yes
smtpd_etrn_restrictions =
     check_client_access cidr:${config_directory}/etrn_networks.cidr,
     reject
smtpd_recipient_limit = 500
smtpd_recipient_restrictions =
    warn_if_reject check_helo_access hash:${config_directory}/access_helo,
    reject_non_fqdn_sender,
    reject_non_fqdn_recipient,
    reject_unknown_sender_domain,
    reject_unknown_recipient_domain,
    permit_mynetworks,
    reject_unauth_destination,
    reject_unauth_pipelining,
    reject_rbl_client dul.dnsbl.sorbs.net,
    reject_rbl_client relays.ordb.org,
    permit
smtpd_timeout = 100s
transport_maps = hash:$config_directory/transport
unknown_local_recipient_reject_code = 550

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