Conversations not grouped by subject in El Capitan mail
I get emails from Fail2Ban on one of the web servers I manage. Each one has a subject of the form "[Fail2Ban] WordPress: banned 45.41.92.66". They're all the same except for the IP address ("45.41.92.66"). Before El Capitan, all the messages with identical subjects, in this case the same IP address, were grouped into a conversation, with a handy dandy counter plainly visible. That made it easy to see which IP addresses were attempting logins so often that I needed to ban them permanently, not just for 10 minutes at a time, as my Fail2Ban is configured to do.
El Capitan mail organizes messages by actual conversations, i.e. messages that are responses to an original, but it doesn't group emails with identical subjects that are not actually part of the same conversation. This is likely correct for many email conversations, but it doesn't work for these Fail2Ban messages. I would love to have a preference to select the old way of grouping by only the text in the subject.
Mail-OTHER, OS X El Capitan (10.11)