Getting email addresses obfuscated in patch attachments created by "git format-patch"

[Jens Schmidt]

Emacs contribution policy recommends to attach patches created by "git 
format-patch".  It seems that the email address contained in such 
patches is *not* automatically stripped by mailman or whatever presents 
the mailing list archives of emacs-devel or bug-gnu-emacs.

Fiddling with "--from" to "git format-patch" does not seem to help, either.

OTOH, I have seen some patches like Paul's in this message:

  https://lists.gnu.org/archive/html/emacs-devel/2016-01/msg01807.html

where his email address is "obfuscated" to

  Paul Eggert <address@hidden>

What causes this obfuscation?  How to configure that?  Manual 
post-processing of the patch with sed?

If it matters, I'd prefer to use Thunderbird to contribute patches ...

Thanks

Jens