I want to block some outgoing emails

[kennio]

I want to block any email send from the accounts under the domain internal.mydomain.com that are sent to any any external email. Example:

Sender -> Receiver -> Result
[email protected] -> [email protected] -> OK
[email protected] -> [email protected] -> OK
[email protected] -> [email protected] -> OK
[email protected] -> [email protected] -> OK
[email protected] -> [email protected] -> OK
[email protected] -> [email protected] -> OK
[email protected] -> [email protected] -> OK
[email protected] -> [email protected] -> BLOCKED

how can I achieve that?

[SKaero]

That should really be handled on the SMTP server.