Your item gets data every 5 seconds (which is very frequent by the way, consider using a longer interval), your trigger used to check the average value over 60 seconds.
Without evaluating every single data value, I'd guess that previous peaks were shorter and the alerting one just happened to be there for a bit longer - to push the average for 60 seconds ...
Do you see the same behavior on the sys.resource_stats system view? Run the following instruction using SQL Server Management Studio (SSMS).
SELECT database_name, AVG(avg_cpu_percent) AS Average_Compute_Utilization
WHERE start_time BETWEEN @s AND @e
GROUP BY database_name
I prefer to trust the above DMV (sys.resource_stats) ...
Short answer: No. The mail format is given by monit. Only content can be changed.
Long answer: Kind of... I had some different ideas on how to distribute messages based on their importance and was not able to find a solution that matched my needs (different message transfer for different priorities). So I came up with a drop-in-replacement for an SMTP ...
Well it seems that v0.11 (which is all you get from Ubuntu 16.04 repos) doesn't have that functionality. Ubuntu 18.04 repos contain v0.15 (still not recent) but there you do get the functionality. No PPA available. Plenty of instructions to manually install newer versions or you can use my Ansible role:
- name: Download package