[CentOS] Mail problem

I have a problem finding the log from centos. I have installed qmail and i receive a lot of infected mails and i can't stop them because i don't know the ip from where they came. I know that in log files it is kept that ip but i havent't find it. In /var/log/ maillog it is a list but it does not have the ip of the mails. Can anyone help me?

Another problem I have with Auto-responder from mail, it's not working at all and i d'ont know why.
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