relaying

I seem to have another problem.I had not allowed a certain domain to relay through me but I am its secondary MX but before I could sort ot out it appears that my machien forwarded the mail without question. This leaves me puzzled. I would love to have relaying denied by default but it doesn't seem to be I thought this was a default setting. the box was a suse 6.1 that I upgraded to 6.4 kernel 2.2.14.