Comment 2 for bug 1994136

It was chosen for a particular reason, the reason being it is nice to
have both title and author's name available in the filename. If you want
to work around Amazon's latest attempt to sabotage sideloading, you will
need to specialize the filename when sending to @kindle.com and
@kindle.cn email addresses. You can probably do that in the send_by_mail
method by examining the to address.