Overall mail volume was way up this month, both spam and non-spam. Percentages were pretty consistent with last month, but there were small drops in effectiveness of DNSBL, server-based content rules and personal rules, resulting in a two point rise in percentage of spam delivered to mailboxes. Extended rules held steady percentage-wise.
There was a change in our MX records this month, as the result of a required change in our strategy for dealing with our servers' dynamic addresses. We swapped the priorities. Configurations are slightly different on the two servers, but DNSBLs are the same and content rules run on the mailbox server, so I really don't think this has anything to do with the slight shift in percentages, but I'm not sure. Our sample size is really too small for me to say that the changes this month are statistically significant.