I'm currently having an issue with exim4. Some mail isn't delivered. I found this in my rejected log.
2012-06-21 10:11:47 H=bart (bart.*.com) [192.168.171.145] F=<info@****.com> rejected RCPT <firstname.lastname@example.org>: all relevant MX records point to non-existent hosts
Is this an issue with my server or rather with the recepients server?