Pardon my French: they can go fuck themselves.
There is no way that I am ever clicking one of those links. If shit is confidential, e-mail is not the medium one should be choosing.
I have a well-kept archive of my e-mail since 2011. Only SPAM and newsletters get thrown out. Rest stays.
I am putting up a webpage with why I consider those mails to be madness, setup a filter with an automated reply and route the received self-distructing mails to /dev/null.
@h3artbl33d @miramarco +1. If I ever get one of those mails I will reply with "sorry, I think your email got corrupted, can you send it again?" π