Till now I've used Git with GitHub personally, but I'm starting to use it professionally with GitLab using a different (company) e-mail address.
In https://docs.gitlab.com/ee/gitlab-basics/start-using-git.html it is explained how to run the
git config --global
Checkout the repository, and use
git config without
The default switch is
That will set new email for this particular repository and will keep your global settings.