公司邮箱服务器是exchange 2013 cu21版本，最近出现往126/163等邮箱发邮件发不出去的情况，报错如下：
returned '441 4.4.1 Error encountered while communicating with primary outbound frontend IP address: "421 4.4.2 Connection dropped due to TimedOut." Attempted failover to alternate frontend, but that did not succeed. Either there are no alternate frontend addresses, or delivery failed to all alternate frontend addresses. The last endpoint attempted was 172.16.103.91:717'
最后的IP是公司内网地址，靠负载均衡设备转换到公网的
sina、qq等邮箱马上就发出去，而发往126/163和其他一些邮箱的邮件就一直堆在队列里，4个小时后发送延迟邮件，2天后发送发送失败邮件，请帮忙分析一下
connectlog内容
2019-01-20T14:25:00.169Z,08D67EA5B8CCEF39,SMTP,sina.com,+,DnsConnectorDelivery 6ffd40cf-9d64-4412-a2db-31b948019860;QueueLength=TQ=1;RN=1;.
2019-01-20T14:25:00.169Z,08D67EA5B8CCEF39,SMTP,sina.com,>,Outbound proxy via EXCHANGE.XXXXX.com[172.16.103.91]
2019-01-20T14:25:00.169Z,08D67EA5B8CCEF3A,SMTP,qq.com,+,DnsConnectorDelivery 6ffd40cf-9d64-4412-a2db-31b948019860;QueueLength=TQ=1;RN=1;.
2019-01-20T14:25:00.169Z,08D67EA5B8CCEF3A,SMTP,qq.com,>,Outbound proxy via EXCHANGE.XXXXX.com[172.16.103.91]
2019-01-20T14:25:00.169Z,08D67EA5B8CCEF39,SMTP,sina.com,>,Established connection to 172.16.103.91
2019-01-20T14:25:00.169Z,08D67EA5B8CCEF3B,SMTP,139.com,+,DnsConnectorDelivery 6ffd40cf-9d64-4412-a2db-31b948019860;QueueLength=TQ=1;RN=1;.
2019-01-20T14:25:00.169Z,08D67EA5B8CCEF3B,SMTP,139.com,>,Outbound proxy via EXCHANGE.XXXXX.com[172.16.103.91]
2019-01-20T14:25:00.169Z,08D67EA5B8CCEF3A,SMTP,qq.com,>,Established connection to 172.16.103.91
2019-01-20T14:25:00.169Z,08D67EA5B8CCEF3B,SMTP,139.com,>,Established connection to 172.16.103.91
2019-01-20T14:25:14.100Z,08D67EA5B8CCEF39,SMTP,sina.com,-,Messages: 1 Bytes: 7816 ()
2019-01-20T14:25:42.445Z,08D67EA5B8CCEF3C,SMTP,126.com,+,DnsConnectorDelivery 6ffd40cf-9d64-4412-a2db-31b948019860;QueueLength=TQ=2;RN=2;.
2019-01-20T14:25:42.445Z,08D67EA5B8CCEF3C,SMTP,126.com,>,Outbound proxy via EXCHANGE.XXXXX.com[172.16.103.91]
2019-01-20T14:25:42.445Z,08D67EA5B8CCEF3C,SMTP,126.com,>,Established connection to 172.16.103.91
2019-01-20T14:28:03.962Z,08D67EA5B8CCEF3A,SMTP,qq.com,-,Messages: 1 Bytes: 7718 ()
2019-01-20T14:30:14.242Z,08D67EA5B8CCEF3B,SMTP,139.com,-,Messages: 0 Bytes: 7598 (Retry)
2019-01-20T14:35:42.496Z,08D67EA5B8CCEF3C,SMTP,126.com,-,Messages: 0 Bytes: 0 (Retry : Connection dropped due to TimedOut)
从这里看出139、sina、qq一下就出去了，126就timedout
returned '441 4.4.1 Error encountered while communicating with primary outbound frontend IP address: "421 4.4.2 Connection dropped due to TimedOut." Attempted failover to alternate frontend, but that did not succeed. Either there are no alternate frontend addresses, or delivery failed to all alternate frontend addresses. The last endpoint attempted was 172.16.103.91:717'
最后的IP是公司内网地址，靠负载均衡设备转换到公网的
sina、qq等邮箱马上就发出去，而发往126/163和其他一些邮箱的邮件就一直堆在队列里，4个小时后发送延迟邮件，2天后发送发送失败邮件，请帮忙分析一下
connectlog内容
2019-01-20T14:25:00.169Z,08D67EA5B8CCEF39,SMTP,sina.com,+,DnsConnectorDelivery 6ffd40cf-9d64-4412-a2db-31b948019860;QueueLength=TQ=1;RN=1;.
2019-01-20T14:25:00.169Z,08D67EA5B8CCEF39,SMTP,sina.com,>,Outbound proxy via EXCHANGE.XXXXX.com[172.16.103.91]
2019-01-20T14:25:00.169Z,08D67EA5B8CCEF3A,SMTP,qq.com,+,DnsConnectorDelivery 6ffd40cf-9d64-4412-a2db-31b948019860;QueueLength=TQ=1;RN=1;.
2019-01-20T14:25:00.169Z,08D67EA5B8CCEF3A,SMTP,qq.com,>,Outbound proxy via EXCHANGE.XXXXX.com[172.16.103.91]
2019-01-20T14:25:00.169Z,08D67EA5B8CCEF39,SMTP,sina.com,>,Established connection to 172.16.103.91
2019-01-20T14:25:00.169Z,08D67EA5B8CCEF3B,SMTP,139.com,+,DnsConnectorDelivery 6ffd40cf-9d64-4412-a2db-31b948019860;QueueLength=TQ=1;RN=1;.
2019-01-20T14:25:00.169Z,08D67EA5B8CCEF3B,SMTP,139.com,>,Outbound proxy via EXCHANGE.XXXXX.com[172.16.103.91]
2019-01-20T14:25:00.169Z,08D67EA5B8CCEF3A,SMTP,qq.com,>,Established connection to 172.16.103.91
2019-01-20T14:25:00.169Z,08D67EA5B8CCEF3B,SMTP,139.com,>,Established connection to 172.16.103.91
2019-01-20T14:25:14.100Z,08D67EA5B8CCEF39,SMTP,sina.com,-,Messages: 1 Bytes: 7816 ()
2019-01-20T14:25:42.445Z,08D67EA5B8CCEF3C,SMTP,126.com,+,DnsConnectorDelivery 6ffd40cf-9d64-4412-a2db-31b948019860;QueueLength=TQ=2;RN=2;.
2019-01-20T14:25:42.445Z,08D67EA5B8CCEF3C,SMTP,126.com,>,Outbound proxy via EXCHANGE.XXXXX.com[172.16.103.91]
2019-01-20T14:25:42.445Z,08D67EA5B8CCEF3C,SMTP,126.com,>,Established connection to 172.16.103.91
2019-01-20T14:28:03.962Z,08D67EA5B8CCEF3A,SMTP,qq.com,-,Messages: 1 Bytes: 7718 ()
2019-01-20T14:30:14.242Z,08D67EA5B8CCEF3B,SMTP,139.com,-,Messages: 0 Bytes: 7598 (Retry)
2019-01-20T14:35:42.496Z,08D67EA5B8CCEF3C,SMTP,126.com,-,Messages: 0 Bytes: 0 (Retry : Connection dropped due to TimedOut)
从这里看出139、sina、qq一下就出去了，126就timedout