1. 核查错误代码：
退信错误代码为：
Blocklist(Block List)
spamhaus
blocked USING FBLW或DNSBL
Too many recipients received this hour
IP frequency Limited(Connection frequency Limited)
Our system has detected an unusual rate of
MTA's poor reputation
RDNS entry
banned sending IP
2. 原因：
发件人IP被列黑，收件方判定为垃圾邮件拒收。
3. 处理方法：
请发件人联系邮箱供应商处理。
