Unfortunately it is not possible using our native Google Sheets integration to overwrite existing rows - our integration will begin adding the data at the first available blank row within your connected spreadsheet.
It may however be possible to use our integration with Zapier to accomplish this instead - the trigger for Update Spreadsheet Row would be able to look for specific rows and overwrite the data found
https://zapier.com/apps/mailparser/integrations/google-sheets
Give that a try and if you need help reach out to us at support@team.mailparser.io