sendmail, avoiding open relay

Hoi ! I´ve a mailserver running at home (for 2 clients - nothing serious), SuSE 7.2. I´ve already restrictet access by using the /etc/mail/access to 192.168 . That´s enough or should i do something more? Background is, i got me this message by my system : ----- The following addresses had permanent fatal errors ----- (reason: 550 relaying to prohibited by administrator) ----- Transcript of session follows ----- ... while talking to smtp.kundenserver.de:

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RCPT To:

<<< 550 relaying to prohibited by administrator 550 5.1.1 ... User unknown Look´s tight to me, or did i miss something important? cu Carsten