How to set mail From as myuser.myhost@mydomain ?

Hi, I'm using RedHat 7.9 with Postfix postfix-2.10.1-9.el7.x86_64 and mailx mailx-12.5-19.el7.x86_64. Postfix config is the simplest one.

Two or three years ago on one server I changed the form of From to myuser.myhost@mydomain globally.

Now I need to replicate this configuration to another server, but I lost my receipts book on an accident and I can't reproduce what I changed.
I think that could not be a postfix configuration problem, but any other
configuration, because I've copied the /etc/postfix/ files to the other server and still not works...

Any help will be appreciated,

Thanks,

Joao Castro