U-Mail邮件系统常见的退信分析

看退信最下面的日志，并按照相应的错误信息进行匹配。
511 sorry, no mailbox here by that name
unknown user account
... User unknown
Name server reports domain name unknown
mailbox unavailable
550 Invalid User:
invalid recipient
No such user here
All recipients are invalid
User unknown in virtual alias table
Mailbox not found
Recipient address rejected: User unknown in relay recipient table
以上信息均为收件人地址错误或者无效，检查收件人地址，检查邮件服务器的域名解析服务器

554 Connection refused(mx). MAIL FROM [[email protected]] mismatches client IP [74.86.11.12].
域名和IP 地址不对应导致的拒收 [上面的域名和IP 地址会变化，类似的情况]，修正您的域名解析，域名解

553 5.7.1 SpamTrap=reject mode, dsn=5.7.1, Message blocked by BOX Solutions (www.box-sol.com)
SpamTrap Technology, please contact the MUSTEK site manager for help: (bkndr63272).
如果出现类似上述的信息是因为您发了不受对方欢迎的信件，导致对方拒收

551 User not local; please try
邮件被GFW 过滤，GFW 是指Great Firewall，中国国家防火墙。尝试将邮件内容打包压缩或者放入OFFICE 文
档内进行邮件传输

Winsock Error 10053 Connection abort.
网络通讯故障

Winsock Error 10060 The connection timed out.
连接超时，网络通讯故障造成

Winsock Error 10061 The connection timed out.
对方服务器拒绝连接，对方服务器主动断开链接，这通常是由国外不活跃的服务器造成的。

452 4.3.1 Out of memory
This message is 60 minutes old; it has 0 minutes left in this queue
Remote queue lifetime exceeded; message placed in retry queue
一般情况下，邮件会进入重试队列进行再次发送，这种情况下对方的邮件服务器一般是Exchange，这是
Exchange 的内部错误造成的。

553 Requested action not taken: no smtp MX
收件人邮箱地址错误，域名无法被解析,检查收件人地址，或者对方域名解析设置错误。

501 syntax.helo hostname
501 Invalid domain name
502 unimplemented command
503 5.0.0 polite people say HELO first
533 relay restriction
544 <>:Recipient address rejected: Relay access denied
传输中的语法错误，原因不明。