[exim] Let users activate/deactive autoreply

Hello.

Exim 3.35 on Debian3 - POP3 and MSOutlook as MUA.

I'm looking for a method giving the individual mail-users the ability to
themselves activate/deactivate the autoreply message filter. I have
looked in the Exim 4 book, but it seems to me that so far it's the
administrator's job to create and activate the autoreply function. This
is not very useful in a everyday situation. Does there exist a solution
for this - maybe the user sending a mail to a specific address?

Regards
Kent Knudsen