Spam problem with Kayako

Every day it seems, I'm getting a ton of bounced mails from an identical domain in my Kayako. It doesn't actually tell me what the original message was, other than that it had bounced. I would ban the particular bounced mail sender (usually postmaster@whatever.com), but the next day it would be another email address, and another one.

What I'm trying to figure out is, why is this happening? Is this being caused by someone sending out junkmail using a support email as the "from"? How can I find out what the original mail was that got bounced? I'm running qmail.

For example, yesterday I had over 800 bounces, all with the same content and sender (postmaster@163.com):

This message is generated by COREMAIL email system.
I'm sorry to have to inform you that the message returned


ģ??ˍ??postmaster@163.com?ēʼ?ςԭҲ??͋?ؠ: postmaster@163.com ӊϤȝ?º

ȧ???˓ВɎʬǫ?ϵ͸җ??˾?ͷ?0-83568090-4(ȫ??24Сʱ?ͻ???f163@188.com

 

 

 

 

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