Debian stable - too stable sometimes even for a server

Debian stable is known for its longterm release schedule. This can be a good thing for certain server applications if it’s more important to keep them running than having problems with cutting edge, but not well tested releases of software. But then, while email certainly is a critical server app, it is in head-head competition with spammers. And the spammers unfortunatelly do not wait for new ways around spam detection until Debian releases a new stable release. We were running Spamassassin with sa-exim on our mail server, the former only 9 months old from october last year. The stats say everything:

Tons of emails, especially in the peaks are said to be clean, although they are not. Switching to Spamassassin from unstable yesterday in the late evening changed the picture completely.