MORE INFORMATION
Collected Status Codes
First Digit
2.X.X Success
4.X.X Persistent Transient Failure 持续性短暂的故障
5.X.X Permanent Failure 永久的错误

Second and Third Digits
X.1.0 Other address status
X.1.1 Bad destination mailbox address
X.1.2 Bad destination system address
X.1.3 Bad destination mailbox address syntax
X.1.4 Destination mailbox address ambiguous
X.1.5 Destination mailbox address valid
X.1.6 Mailbox has moved
X.1.7 Bad sender's mailbox address syntax
X.1.8 Bad sender's system address

X.2.0 Other or undefined mailbox status
X.2.1 Mailbox disabled, not accepting messages
X.2.2 Mailbox full
X.2.3 Message length exceeds administrative limit
X.2.4 Mailing list expansion problem

X.3.0 Other or undefined mail system status
X.3.1 Mail system full
X.3.2 System not accepting network messages
X.3.3 System not capable of selected features
X.3.4 Message too big for system

X.4.0 Other or undefined network or routing status
X.4.1 No answer from host
X.4.2 Bad connection
X.4.3 Routing server failure
X.4.4 Unable to route
X.4.5 Network congestion
X.4.6 Routing loop detected
X.4.7 Delivery time expired

X.5.0 Other or undefined protocol status其它或者不明确的通讯协议状态
X.5.1 Invalid command 无效的指令
X.5.2 Syntax error  语法错误
X.5.3 Too many recipients 太多的接受者
X.5.4 Invalid command arguments  无效的指令要旨
X.5.5 Wrong protocol version  错误的通讯协议版本

X.6.0 Other or undefined media error 其它或者不明确的环境,媒体错误
X.6.1 Media not supported 环境媒体不支持
X.6.2 Conversion required and prohibited 变换命令和妨碍
X.6.3 Conversion required but not supported 变换命令但不支持
X.6.4 Conversion with loss performed 变换包括遗失执行
X.6.5 Conversion failed 变换错误

X.7.0 Other or undefined security status 其它或者不明确安全状态
X.7.1 Delivery not authorized, message refused传送不经授权,讯息垃圾
X.7.2 Mailing list expansion prohibited邮件名册宽度妨碍
X.7.3 Security conversion required but not possible
X.7.4 Security features not supported
X.7.5 Cryptographic failure
X.7.6 Cryptographic algorithm not supported
X.7.7 Message integrity failure 讯息完全故障
部分已翻译,部分一看就懂,部分我都看不懂,哈哈!

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