sendmail relaying denied

[cba2_(_at_)_gouda_(_dot_)_netcity_(_dot_)_de]

Hi,

i'm new to OpenBSD, so sorry if this is a stupid question:

To allow incoming mail I changed the default value of sendmail parameters
in /etc/rc.conf to:     sendmail_flags="-bd -q30m"

when I start sendmail as root by hand, everything works fine, but after 
rebooting, sendmail does not accept incoming mail:

550 5.7.1 <user_(_at_)_machine_(_dot_)_domain_(_dot_)_de>... Relaying denied

Is there anything else I have to change except /etc/rc.conf to get sendmail
work after reboot? I'm using 2.7 release. 

Thanx very much for any hint,

Christoph