Hi there,
since a couple of weeks (maybe month?) we have an issue with the "Changes in the last 24 hours" mails. These mails are sometimes sent, sometimes not. We can't see any reason and have no clue where exactly to look for an error.
In the past we rebooted our machine and the it worked for a short time. Now we want to find the reason and finally solve the problem 
All other mail notifications are working without problems
Any ideas where to look why only the "24 hours" mails are stuck?
Confluence 6.15.6 running on Ubuntu (16.04 LTS) 
BR
Chris