1，偶尔收件还是延迟 有时候甚至要延时好几个小时
2，国内的用户有个别邮箱会出现问题，比如收到mail delayed的邮件
下面贴上mail delayed发来的邮件，忘老司机指点一二
This is the mail system at host mx-cn.XX.com.
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# THIS IS A WARNING ONLY. YOU DO NOT NEED TO RESEND YOUR MESSAGE. #
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Your message could not be delivered for more than 1 hour(s).
It will be retried until it is 5 day(s) old.
For further assistance, please send mail to postmaster.
If you do so, please include this problem report. You can
delete your own text from the attached returned message.
The mail system
<XX@mx-cn.XX.com> (expanded from
<XX@cn.xx.com>): host
mx-cn.XX.com[/var/lib/imap/socket/lmtp] said: 452 4.2.2 Over
quota SESSIONID=<mx-cn-25412-1468210608-1> (in reply to RCPT TO command)