> the first area called Netmail with Nodenumber 0 (which is my Fidonet number).

This is correct.

> But If I want to send a netmail to another net the message is addressed to
> the other net (correct) but the origin is my fidonet number. How can fix that
> please.

Check your bcfg4://global/fidonet/general AKA matching rules. First matching
rule will be used. For example:

0:  2:222/2.0     ^[1-6]:
1:  123:456/7.0   ^123:
2:  40:42/42.0    ^42:

--- BBBS/Li6 v4.10 Toy-3