The maximum number of delivery attempts has been reached 解决方法一例
 

问题描述：
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某公司服务器向客户Exchange 2010服务发邮件时老是不成功，有时退信内容为：

The maximum number of delivery attempts has been reached

或是

The reason of the delivery failure was:417 Temporary delivery error

解决办法：
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根据退信搜索到下面这个资料：

SMTP Connector rejected an incoming connection - the maximum number of connections has been reached

SMTP Connector rejected an incoming connection - the maximum number of connections has been reached

根据提示修改默认连接器的进站数，如下命令：

set-ReceiveConnector -Identity "Default" -MaxInboundConnectionPerSource 500

即解决问题。

PS：客户的环境还有一个冰峰的行为管理器，也同时禁用了。