请教:mx记录的问题

earth901

如果一个邮件系统有多个mx记录，出现下面情况会如何投递？

abc.com.             86400   IN      MX      10 mx1.abc.com.
abc.com.             86400   IN      MX      20 mx2.abc.com.
abc.com.             86400   IN      MX      20 mx3.abc.com.
abc.com.             86400   IN      MX      10 mx4.abc.com.
abc.com.             86400   IN      MX      10 mx5.abc.com.


比如发信服务器选择发到mx1，而mx1挂掉了，发信服务器会向另一个优先级为10的服务器投递，还是发送到优先级为20的服务器，再由20的邮件服务器转发给其他优先级为10的服务器呢？

earth901

啊？2821里不是说974被废除了么？
那这段话
If a matching record is found, all records at that preference level and higher-numbered ones MUST be discarded from consideration.
具体到底是啥意思啊？

ailms

可能的顺序应该是

1）mx1，mx4，mx5 或者 mx4，mx5，mx1 ，或者 mx5，mx1，mx4

2）然后是 mx2，mx3 或者 mx3，mx2

[ 本帖最后由 ailms 于 2006-8-7 13:22 编辑 ]

ailms

If a matching record is found, all records at that preference level and higher-numbered ones MUST be discarded from consideration.

这个和 lz 的问题不是同一个意思，而是指如何防止 mail loop 的

earth901

恩，在RFC2821中确实提到了“ If a matching record is found, all records at that preference level and higher-numbered ones MUST be discarded from consideration. ”而且“It obsoletes RFC 821, RFC 974, and updates RFC 1123 ”
看来应该是按abel兄说的这样，谢谢！

abel

原帖由 ailms 于 2006-8-7 09:38 发表
这就是 RFC974 中摘出来的

1. 
   
2. RFC 2821
   
3. 
   
4.    Multiple MX records contain a preference indication that MUST be used
   
5.    in sorting (see below).  Lower numbers are more preferred than higher
   
6.    ones.  If there are multiple destinations with the same preference
   
7.    and there is no clear reason to favor one (e.g., by recognition of an
   
8.    easily-reached address), then the sender-SMTP MUST randomize them to
   
9.    spread the load across multiple mail exchangers for a specific
   
10.    organization.
    

复制代码

http://www.rfc-editor.org/cgi-bin/rfcsearch.pl?searchwords=rfc2821&opt=All+fields&num=25&format=ftp&orgkeyword=974&filefmt=txt&search_doc=search_all&match_method=prefix&abstract=absoff&keywords=keyoff&sort_method=newer

Obsoletes RFC821, RFC974, RFC1869, RFC10
Errata

ailms

这就是 RFC974 中摘出来的

Note that
   multiple MXs may have the same preference value.  In this case, all
   MXs at with a given value must be tried before any of a higher value
   are tried.  In addition, in the special case in which there are
   several MXs with the lowest preference value,  all of them should be
   tried before a message is deemed undeliverable.

ailms

写错了，是974

abel

794 ?

ailms

RFC794