"vacation"-message only works when @me address is used, while most people use my @mac

Hi,
since I'm leaving on a holiday I wanted to set a standard "out of the office etc." reply message. I did that on the Mobile me page, under preferences/vacation.
When sending a message to my mac.com mail address I don't receive the "out of the office" message. When I send it to the me.com addres, I do.
Most people still only use my mac.com address. How I can set the same message for the mac.com?
I thought the mac.com and me.com address were synchronized.

Thanks in advance for your help.

Stefaan