收到退信如何处理？

如果您发送的邮件被退回，您的收件箱会收到一封退信。 通过判读退信里关键字，可以了解退信的主要原因。下面是一些常见的退信信息：

收件人地址错误：

550 Mailbox not found.

550 User not found:

550 Mailbox unavailable or access denied

550 Invalid Addresses;

450 Requested action not taken:

550-5.1.1 The email account that you tried to reach does not exist. Please try double-checking the recipient's email address

收件人域名拼写错误：

There are no DNS entries for the hostname Domain : qq.con.

Temporary problem looking up mail server for host: Domain : qq.cn.

网络连接异常：

Couldn't connect to host..

connect timed out

因收件方反垃圾拒收：

554 rejecting banned content

554 5.7.1 Too many spam complaints

554 Service unavailable; Client host blocked using Barracuda Reputation;