Vacation and Aliases

I am running a postfix mail server (2.0.014) hosting several domains. The
problem is when users who have multiple aliases start using vacation. It
only replies to the original name and not the aliases. Now I can force it
to reply to an alias by using the -a switch, but this would require users
to contact the help desk rather than using the vacation interface in
Horde/Imp. Needless to say, my help desk would not be pleased.

How are all of you handling this situation?
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Terry Poperszky