Emails being sent from my network

[Langdon Green]

Hi guys,   I am having a bit of trouble with some dodgy emails getting sent to my friend...they are strange, not just normal spam, the emails have information that is from my company web site (hosted off site)   Anyway, the header of the emails has this line:   Received: from Wzk ([MYIP]) by out.somewhere.net   Does this indicate a computer on my network has be hacked, and is emailing this? I am running a debian router with an ipchains firewall, on a small masqueraded home network, with a debian file server running samba.   I have had a look on the router for anything suspicious, but there is just too many things it could be.  I am in the process of making a new router that will have IDS installed (I know I know, but I was in a rush:)   Any Ideas?   Langdon