Log processing rule for masking an email within a json object

[zahra-khan]

Here is my log processing rule. Can anyone tell me what I am doing wrong?
I am really struggling to get this to work. I have stripped down my actual JSON object a lot, but I can't get it to work. 

[marco_irmer · Accepted solution]

Two things per the documentation:
1. Whenever the content or any other attribute is to be changed, it has to be declared as INOUT (writable) with the USING command.

2. When replacing, the input and output fields need to be the same. For instance, if you're modifying 'content', then your FIELDS_ADD command should add a  field called 'content' instead of 'modified_content'. This way the newly formed field replaces what was there before.