How to Delete App data in Windows 10 Mobile?

[IndianFalcon]

I upgraded to Windows 10 Mobile using the Upgrade Advisor tool for my Lumia 640 XL.
Current Build : 10.0.10586.318 Version : 1511

My phone memory is completely used up. When I look at storage the size of the applications is huge. Mail and Calendar uses 1.57 GB of space Rest all are around 50-100 MB.

When I installed these apps the size was not this big. I understand the data being generated but is there a possibility of removing only app data (as in Android) or is reset the only option.

 

[Ma Rio]

Unfortunately there is no way yet to do that. It's comming in the aniversary update (yet it's still up to the developper to enable that functionality).
As for you, try changing your sync settings for your mailboxes. Set it so that it only syncs the mail from last month.