Relaying mails from internal hosts

Hi,I promis, I read a lot of entries here in this forum about this but nothing seems to work for me.

I have one PC who has a software installed which need to send a mail via an SMTP-Server. I got my server by now to acccept the connection, but then get the message

Router: user@our-domain.com is restricted from sending mail through server Server/Domain/DE

I tried all kind of combinations in the Inbound and Outbound Control, but nothing works. Can somebody maybe give me a working setting. I’m a little frustrated after hours of testing.

Thanks

Oliver