How to delete a google apps script service
Find the URL to the script url in the script editor i.e:
https://script.google.com/macros/d/MS3-PFwnUdYw7_bQF3y8BJte_1Q7n6BNa/edit
Remove edit from url and replace with manage/uninstall
https://script.google.com/macros/d/MS3-PFwnUdYw7_bQF3y8BJte_1Q7n6BNa/manage/uninstall
Click uninstall and that should be it!
Strange. Maybe, Try checking if the trigger is still there:
Open a spreadsheet then go to Tools -> Script Editor, then on the editor window go to Edit -> All your triggers... and see if the gmail meter method is still listed there. If so, delete it.
After you delete the script, look for it in the trash folder and delete it from there as well. This has worked for me; no other steps are necessary.