Special procmail problem

I have a email domain that leads to only one mailbox.
How can you (IF you can) make procmail to see to what address was the mail
message
ment for, and then save it to UNIX file in the same system?

For example:

domain @esgroup.pp.sci.fi is forwarded to mbox jth(_at_)sci(_dot_)fi(_dot_)

how can you make procmail see whether the message is sent to
 
        jouni(_dot_)honkala(_at_)esgroup(_dot_)pp(_dot_)sci(_dot_)fi
        or
        jth(_at_)sci(_dot_)fi
        or
        esgroup(_at_)esgroup(_dot_)pp(_dot_)sci(_dot_)fi
        or somewhere else?