Make sure you have the line mdns off in /etc/host.conf on your incoming SMTP servers.
One of my colleagues in our network engineering team discovered today that ppswitch was spewing multicast packets, much to our surprise. It turns out that recent versions of glibc have quietly added support for multicast DNS to the resolver. Multicast DNS is part of Apple's zeroconf networking system (aka Bonjour, previously known as Rendezvous), and it takes over responsibility for host names ending in .local. See it in action by typing strace ping foo.local and observe it sending a DNS query to the class D multicast address 224.0.0.251. A significant number of the DNS lookups that our MXs do (10,000 per day) are names ending in .local which trigger mdns lookups. These names (mostly HELO domains) do not come from machines named via zeroconf: they are mostly Small Business Server installations which have followed Microsoft's recommendations for choosing a domain name. See http://www.zeroconf.org/ and http://support.microsoft.com/kb/296250 Tony. -- <[EMAIL PROTECTED]> <[EMAIL PROTECTED]> http://dotat.at/ ${sg{\N${sg{\ N\}{([^N]*)(.)(.)(.*)}{\$1\$3\$2\$1\$3\n\$2\$3\$4\$3\n\$3\$2\$4}}\ \N}{([^N]*)(.)(.)(.*)}{\$1\$3\$2\$1\$3\n\$2\$3\$4\$3\n\$3\$2\$4}} -- ## List details at http://lists.exim.org/mailman/listinfo/exim-users ## Exim details at http://www.exim.org/ ## Please use the Wiki with this list - http://wiki.exim.org/