After some more conversation with the SpamAssassin upstream the MIRRORED.BY has been successfully modified to exclude the stale server in the pool. I haven't seen a failure from any of my machines in the last day. I think the current problem has been averted.
$ wget -q -O- http://spamassassin.apache.org/updates/MIRRORED.BY # test mirror: zone, cached via Coral #http://buildbot.spamassassin.org.nyud.net:8090/updatestage/ #Removed on 2012-09-26 per bug 6838 #http://daryl.dostech.ca/sa-update/asf/ weight=5 http://www.sa-update.pccc.com/ weight=5 http://sa-update.secnap.net/ weight=5 Bob
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