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December 18, 2002
产生mail loop的原因及解决方案
Mail loop是一个很常见，但有时却又让人很难发现故障所在的问题。如何去发现和解决呢？这里以我自己遇到的mail loop问题为例子，来分析一下个中原因。
日志里关于mail loop的内容如下：
Dec 18 18:35:20 smtp postfix/cleanup[9526]: 4846417D5E:
message-id=<20021218223122.C5B6C680A@smtp.hzqbbc.com>
Dec 18 18:35:20 smtp postfix/qmgr[9342]: 4846417D5E:
from=<hzqbbc@hzqbbc.com>, size=1431, nrcpt=4 (queue active)
Dec 18 18:35:20 smtp postfix/local[9585]: C4F5117D5C:
to=<postmaster@192.168.0.27>, relay=local, delay=33,
status=sent (forwarded as 4846417D5E)
Dec 18 18:35:20 smtp postfix/local[9585]: 4846417D5E:
to=<postmaster@192.168.0.27>, relay=local, delay=22,
status=bounced (mail forwarding loop for postmaster@192.168.0.27)
这里ldap的entry是：
dn: mail=postmaster@overtheland.com,virtualDomain=overtheland.com,o=myldap
objectClass: top
objectClass: MailAccount
objectClass: MailAlias
accountActive: TRUE
mailacceptAction: RELAY
mail: postmaster@overtheland.com
homeDirectory: overtheland.com/postmaster
mailbox: overtheland.com/postmaster/Maildir/
quota: 20971520S,1000C
maildrop: postmaster@smtp.overtheland.com
maildrop: root@overtheland.com
maildrop: postmaster@192.168.0.27
maildrop: hzqbbc@redhut.net
相应的ldap设置是：
=================================================================
ldapstaraliasfixup_query_filter = (&(maildrop=%s)(accountActive=TRUE))
ldapstaraliasfixup_result_attribute = mail
~~~~~~~~~~~~
ldapforwardings_query_filter =(&(mail=%s)(accountActive=TRUE))
ldapforwardings_result_attribute = maildrop
~~~~~~~~~~~~~
这里为什么有问题呢？很简单的解释：我发信给root@192.168.0.27。按照alias部分的ldap
设定，信笺应该投递给postmaster@overtheland.com。。确实正常的投递了。不过问题也就
来了。因为还设置了forward部分，而它expect的是maildrop属性的值，这里maildrop有多个值
其中包括了root@192.168.0.27，这样forward时除了给那些非root@192.168.0.27的地址发信外
还会给root@192.168.0.27自己发信。。。这个就产生loop了（看log可看到）
之后。由于root@overtheland.com并不存在机器上（只是一个postmaster@overtheland.com）
的一个alias）。而这时pipe将信笺给了maildrop，maildrop查ldap时并没有办法查得出
root@overtheland.com就是postmaster@overtheland.com（这个是maildrop的ldap部分缺陷，
有待改进）。因此返回user unknow。这个时候自然得给发信者。。。
之后就是很混乱的loop及bounce 信笺了。所以注意一点。forward及alias必须分开来
设置（用不同属性）否则就麻烦了。
而有关类似的mail loop问题的讨论，在Postfix邮件列表上非常多，这里仅举一例：
寄件者：Dirk Datzert (Dirk.Datzert@rasselstein-hoesch.de)
主旨：postfix and ldap
View this article only
新闻群组：mailing.postfix.users
日期：2001-04-10 14:54:04 PST
Hi all,
I have a postfix question with ldap using:
How can I configure aliases_maps and virtual_maps for the following
issue:
a user has a local 'mail'/'mailalternateaddress' with 'uid' and an
'mailforwardingaddress'
I could configure for local delivery:
alias_maps: ldap:aliases
aliases_query_filter = (│(mail=%s)(mailalternateaddress=%s))
aliases_result_attribute = uid
If a user has no local address I can forward:
virtual_maps: ldap:forwarders
forwarders_query_filter = (│(mail=%s)(mailalternateaddress=%s))
forwarders_result_attribute = mailforwardingaddress
Now my question:
How can I configure postfix to do both for one user: delivery local and
forward ?
Thanx,
Dirk
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第 4 条留言
寄件者：LaMont Jones (lamont@hp.com)
主旨：Re: postfix and ldap
View this article only
新闻群组：mailing.postfix.users
日期：2001-04-10 16:04:07 PST
> aliases_query_filter = (│(mail=%s)(mailalternateaddress=%s))
> aliases_result_attribute = uid
> virtual_maps: ldap:forwarders
> forwarders_query_filter = (│(mail=%s)(mailalternateaddress=%s))
> forwarders_result_attribute = mailforwardingaddress
> Now my question:
>
> How can I configure postfix to do both for one user: delivery local and
> forward ?
result_attribute is a _LIST of attributes, so if you can get the changes
down to one map (merge alias and virtual), then you can just say:
_result_attribute = uid mailforwardingaddress
Untested, your mileage may vary, but we have similar things working in
production.
lamont
Wietse关于mail loop的解释
m 如何防止mail loop？看看wietse如何说的 ( 2003年1月2日21:28 )http://groups.google.com/groups?hl=zh-CN&lr=&ie=UTF-8&inlang=zh-CN&threadm=a3f25j%24urn%241%40FreeBSD.csie.NCTU.edu.tw&rnum=6&prev=/groups%3Fq%3Dmail%2Bloop%2Blist%2Bgroup:mailing.postfix.users%26hl%3Dzh-CN%26lr%3D%26ie%3DUTF-8%26inlang%3Dzh-CN%26selm%3Da3f25j%2524urn%25241%2540FreeBSD.csie.NCTU.edu.tw%26rnum%3D6
You must list myhostname under mydestination:
mydestination = $myhostname localhost.$mydomain ...
Otherwise you will have a mail loop.
Wietse
寄件者：Wietse Venema (wietse@porcupine.org)
主旨：Re: mail loops back to myself
View this article only
新闻群组：mailing.postfix.users
日期：2003-01-18 17:29:08 PST
Is clanetsys.homeunix.net listed in mydestination? See the
main.cf file comments for guidance.
Is clanetsys.homeunix.net listed in virtual_alias_domains?
See the virtual(5) manual page for guidance.
Is clanetsys.homeunix.net listed in virtual_mailbox_domains?
See the VIRTUAL_README file for guidance.
If the domain is not listed in any of the above, then mail
will loop.
Wietse
Posted by hzqbbc at December 18, 2002 05:58 PM