Personally I think it's a good way to prevent some email spammer to get your email address.
So to encode your email,
$ echo "firstname.lastname@example.org" | base64
It will return the encoded string:
To decode, do:
echo "eW91cmVtYWlsQGRvbWFpbi5jb20K" | base64 -d
It will return exactly your information.
Hope it helps!