When letting Google or Yahoo store the email in the cloud one assumes that _they_ keep a backup - indeed that there are several copies of the messages stored - so this seems weird.
It contains my home address, mobile number and so on, so I'd rather not post it.
But it looks like a plain article class LaTeX document, except that I changed the margins and the font (Palatino instead of Times). If you want a more sophisticated layout you can customize the LaTeX-specific options; they'll be ignored when you export to other formats.
A lot of people have said that our brains are wired differently. I highly recommend Delusions of Gender by Cordelia Fine, it's looking into exactly those claims:
So "opt-in by default" doesn't make any sense.
However, I do see this opposite usage increasingly often, which means "opt-in" shouldn't be used any more.
Using "on by default", "enabled by default", "off by default", "disabled by default" would be clear and make sense.