原因为收件服务器暂时繁忙或故障导致无法投递，建议稍后再重新尝试。
退信提示：“delivery temporarily suspended：connect to mail.abc.com[xxx.xxx.xx.xx]：Connection timed out”
2019-10-23 11:22:00
原因为收件服务器暂时繁忙或故障导致无法投递，建议稍后再重新尝试。
2017-06-06
2019-10-29
退信提示：“550 5.7.1 Recipient not authorized, your IP has been found on a block list”
2019-10-23
2011-10-28