Unable to update commiter email id and name; On updating Email id and names, fields are updated but emails still sent from old sender

I wish to update the commiter email id on one of the app servers. I tried to do so using below:

git config --global user.name "John Doe"

git config --global user.email "John.Doe@example.com"

I verified the change of email on the server using below:

git config --global user.name

git config --global user.email

It displays the new email and name correctly. However, whenever I am doing a git commit and push, it is still sending it from the old email address.

I even tried to commit using --amend as below but it is still sending the email from old email address.

git commit --amend --author="Philip J Fry <someone@example.com>"

This is on GitLab CE 12.4.0