If you want to modify only the first commit, you may try git rebase and amend the commit, which is similar to this post: How to modify a specified commit in git?
And if you want to modify all the commits which contain the raw email, filter-branch is the best choice. There is an example of how to change email address globally on the book Pro Git, and you may find this link useful http://git-scm.com/book/en/Git-Tools-Rewriting-History