Somehow this got broken in 6.5. I have tried to look into it, but I am not smart enough at this time to know what is wrong. I looked at the rpm changelogs and it looks like the function is still present in 6.5, but it just doesn't work. I even built a 6.01 box and set up the maillog which worked, then upgraded to 6.5rc1 and that funtion broke. I was going to send a bug report, but I am not sure how many people are working on 6.5 bugs now that the CentOS port is going pretty well. I have been trying to look at the 6.5 bugs, but it's a slow process for me.
JB