Rule for handling internal mails


I want to create a rule for automatic handling e. g. password questions .

So I build a rule "if there is a new mail and it contains the keyword 'password' then answer with a mail containing 'first help informations'."

But I want to send the aswer only to senders of my own domain.
Filter rules will only allow to look into the "from" field, but I didn't find a way to select only incoming mails from senders with an email address *

The special holiday rule in GW will handle the difference between internal (groupwise) senders and external senders.

How can I do this in GW self made rules?

Thanks for help,