[Web-cyradm] How do I assign aliases like postmaster

[Wim Bakker]

Hai

I want to route mail for postmaster at domain.tld and
the likes to an accoount in domain.tld.
The webinterface won't let me do that , whatever
I try it says :
  Reserved Emailadress, request cancelled

How am I supposed to arrange for mail directed at
postmaster at ... go into the inbox of one of the
accounts from domain.tld.

Thanks

Wim Bakker