Hi Kaisa,
As i am new to quick base i don't know exactly whats your requirement. From my knowledge i thought i can have a contribution on some logic. So you could have a hand on the situation.
Create Two Tables
Let it be
Parent , Child
For an example
Parent Fields:
id
name
email id
Child fields:
original id
original name
original email id
Create a relationship between both tables like one Child record to many Parent records
[Give lookup of original email id]
So create the record from Child and and add child record for corresponding to Parent
So based on the relationship . The record on the Parent will have the Child lookup original email id field
Now create a formula email field with the below formula:[Example Field Name: Match Email field]
If([Email Id]<>[Child - Original Email Id], "Not Matching","Matching")
Email id : Parent field
Child - Original Email id : Relationship lookup field
Now the records will check and give the status as matching or not matching
At Last create a report: Table Report
On Filters Give the filter as
Match Email field is equal to the value Not Matching
Now you will get the report with mail id's that are not matching
