With the upgrade from Debian Jessie to Stretch, the Cacti package went from 0.8.8b to 0.8.8h. A problem I had - and apparently a few other people, according to the Cacti forums - was that Cacti 0.8.8h in combination with the thold v0.5 plugin and Stretch refused to send “Downed device notifications”, or threshold warnings in general. Sending test emails with the Cacti settings plugin worked just fine, but that was it.
