Let me share a POC I did in BOXI3.1 with efashion universe :
My initial Table:
It has break in Year. CountVariable is having formula: =Count([Lines];All)Where ([Quarter]="Q1")
This is similar to Email Sent in your case. Now I need to sort the block based on the subtotals.
Now, click on Year column and uncheck the sort option in break properties.
Now create a variable for subtotal which we will use for sorting.
v_Subtotal =Sum([CountVariable] In Break)
Now is the tricky part. Select Year column and add a ranking.
Use top N where N >= number of Years. Here you need to assume a maximum and use a sufficiently large value. I have only 3 years in my report and I have used top 10 as I assume no of years will never cross 10.
Apply the sort based on v_Subtotal variable that we created already.
Here is the final result:
The years are now sorted based on subtotal.
Try it and let us know if you are able to achieve what you want.
Regards,
Arijit