First i had this Problem, no mails were forwarded:
Feb 11 15:58:20 mx postfix-local[15946]: Unable to forward original message. sendmail status: 255
Feb 11 15:58:20 mx postfix-local[15946]: Unable to send mail for: c.name@externaldomainde
Feb 11 15:58:20 mx spamd[8212]: prefork: child states: II...
main.cf
# See /usr/share/postfix/main.cf.dist for a commented, more complete version
# Debian specific: Specifying a file name will cause the first
# line of that file to be used as the name. The Debian default
# is /etc/mailname.
#myorigin = /etc/mailname
smtpd_banner = $myhostname ESMTP...