mail forwarding in OS X, how to?

[Eduard Hoenkamp]

In other unixes I am familiar with, users needs only create a .foward 
in their home directory containing the forwarding address. That does 
not seem to work in OSX (why not?), where the system administrator 
has to change the /etc/aliases, and run newaliases. Perhaps I am 
overlooking something in the sendmail.conf? Thank you for advice or 
suggestions so users can set forwarding on their own. Eduard.