The Messaging Gateway conduit log shows errors indicating that it is unable to fetch ruleset data from aztec.brightmail.com due to a failed temporary redirect.
2015-05-19T10:31:16+09:00 (ERROR:27335.2463053568): Error from web server 307 - Temporary Redirect : unable to GET: https://aztec.brightmail.com/customer/rules/hashes.vcdiff/1/1445587
This error occures when a redirect URL provided by the rules infrastructure no longer points to an existing update. This usually only occurs when a Messaging Gateway system has been offline for an extended period of time and the rule sets on disk are significantly out of synchronization with the latest rule data.
Since this generally only occurs when rule sets are significantly out of synchronization, the simplest means of resolving the issue is to for the Messaging Gateway to download the full set of rule data by deleting all rules on disk. Since this leaves the messaging gateway without an operating set of rules, it is best to pause message acceptance during this process: