My SMTP server is being abused because external adresses can send emails to adresses like all@mydomain.com, dev@mydomain.com etc...
I would like to restrict the usage of those adresses only by internal users ( could be from network ) that have the same domain name like john@mydomain.com.
With these restriction external user like joe@externaldomain.com couldn't send emails to all@mydomain.com but john@mydomain.com could. And joe@externaldomain.com could send an email to john@mydomain.com.
I hope that it is clear enough... I realy don't know how to implement that in Postfix.