Relay access denied when using SMTP to external recipients POSTFIX FREEBSD

i am trying to send an email with my freebsd server using postfix and dbmail to an external adress.

I have noticed the following things:

MYSERVER -> MYSERVER = OKAY

EXTERNALSERVER -> MYSERVER = OKAY

MYSERVER -> EXTERNALSERVER = ERROR(454 4.7.1 Relay access denied)

Why do i get this error? i think it has something to do with my main.cf

MAIN.CF

queue_directory = /var/spool/postfix

command_directory = /usr/local/sbin

daemon_directory = /usr/local/libexec/postfix

data_directory = /var/db/postfix

mail_owner = postfix

default_privs = nobody

myhostname = server.domain.nl

mydomain = domain.nl

myorigin = $mydomain

inet_interfaces = all

virtual_transport = dbmail-lmtp:localhost:24

virtual_mailbox_domains = domain.nl

unknown_local_recipient_reject_code = 550

mynetworks = 127.0.0.0/8 [::1]/128

smtpd_helo_required = yes

strict_rfc821_envelopes = yes

debug_peer_level = 2

debugger_command =

PATH=/bin:/usr/bin:/usr/local/bin:/usr/X11R6/bin ddd $daemon_directory/$process_name $process_id & sleep 5

sendmail_path = /usr/local/sbin/sendmail

mailq_path = /usr/local/bin/mailq

setgid_group = maildrop

html_directory = /usr/local/share/doc/postfix

manpage_directory = /usr/local/man

sample_directory = /usr/local/etc/postfix

readme_directory = /usr/local/share/doc/postfix

inet_protocols = ipv4

smtpd_recipient_restrictions = permit_sasl_authenticated permit_mynetworks reject_unauth_destination

Thanks in advance