How can I filter mails with this subject?

[redprive]

Hi,

I have a problem. One client receives in mail account a lot of mails with next subjects:

"Failure notice..."
"Delivery..."
etc...

I know these mails arrive automaticly to his account because administrator's system servers send this mails to alert about problems, but I want filter them any way to my client don't receive.

I have created a rule file to spamassassin and it functions very well, but the problem is that account that has sent this mail is marked spam always and I don't want it.

Could you help me?

Thank you very much