Found the solution myself after hours of 'googling'. The Kernel 2.4 has a bug|feature: A ipv6 connection is automaticly a ipv4 connection. So if sendmail tryes to open a port twice it's locked. If you enable only inet6 inet4 is automaticly enabled. Solution for the mc file: DAEMON_OPTIONS(`Port=smtp, Name=MTA, Family=inet6') (and no line about inet) -Benoit-