git seems to have changed the way .mailmap works.

Now you only specify the email address to map from, not another
email address to map to. This way only the name is canonicalized.

.mailmap

@@ -1,9 +1,9 @@
-Jeff Bezanson <[email protected]> <[email protected]>
-Jeff Bezanson <bezanson@post.harvard.edu> <bezanson@mathstation045.mit.edu>
-Jeff Bezanson <bezanson@post.harvard.edu> <bezanson@mathstation049.mit.edu>
-Jeff Bezanson <bezanson@post.harvard.edu> <bezanson@mathstation186.mit.edu>
-Jeff Bezanson <[email protected]> <jeff@lagann.(none)>
-Jeff Bezanson <bezanson@post.harvard.edu> <bezanson@scooby-doo.csail.mit.edu>
-Stefan Karpinski <[email protected]> <[email protected]>
-Stefan Karpinski <stefan.karpinski@post.harvard.edu> <stefan.karpinski@gmail.com>
-Viral Shah <[email protected]> <[email protected]>
+Jeff Bezanson <[email protected]>
+Jeff Bezanson <[email protected]>
+Jeff Bezanson <[email protected]>
+Jeff Bezanson <[email protected]>
+Jeff Bezanson <jeff@lagann.(none)>
+Jeff Bezanson <[email protected]>
+Stefan Karpinski <[email protected]>
+Stefan Karpinski <[email protected]>
+Viral Shah <[email protected]>