Once someone sends me an email, barring any prior agreement, it's mine. I may not own the ideas therein, but I certainly can claim enough ownership that the sender destroying the email irrevocably, without my consent, should raise some flags.
I'm seeing parallels with those useless "this email is confidential, private property, etc." footers that people stick on their emails.
"NOTE: This email's content (shown below) will self-destruct after being viewed.
-Sent w/ ghostmail <http://www.ghostmailapp.com/>
And nothing else. Plus when I re-open the message I get the same thing.
Not loading remote images is a norm for email clients.
Implementing the self destruction protection on the client is problematic (even in the case of SnapChat) because the end user is in control of the client. So if users are motivated enough they'll be able to circumvent any protections you implement.
The nice thing is that most users are not motivated enough to do what's necessary to retrieve the self-destructing messages. It's a lot easier to save the message when sent to a web client but it's still beyond the ability of most users.
So no these applications aren't providing real security but it's close enough for the types of messages that I assume people are sending.
I see the email space and the SMS/text space diverging into very separate use cases: email for long form communications that, if anything, are to be saved and filed; SMS for short-form communications that are disposable (literally, in the case of Snapchat, or figuratively). I get that there are long-form communications that are sensitive, and that we sometimes wish wouldn't stick around forever. But what proportion of all email conversations do we think this use case represents?
Note that this depends on the recipient's email client making a request for the image, which, thankfully, most clients provide a way to turn off.
I think the money just wasn't there for public use.
Think how someone like General Patreaus could have benefited! He trusted Broadwell (perhaps his main mistake), but unfortunately for him the email hung around long enough for the FBI. :))
Also, docs say email is destroyed as soon at is read. No 7 days (couldn't find that).
the server makes a note not to supply that image ever again
The wording could be more precise.
Obviously the person can choose to save the image but you could also not destroy your ATM Pin Letter and/or even photocopy it.
"That being said, you should always be careful. We recommend you do not send any seriously sensitive information through Ghostmail and refrain from corresponding with people you do not trust."
That being said, congrats on building something. I still haven't gotten that far.
While most email systems communicate over encrypted protocols, very few encrypt their data store.
For security's sake, please never send your SSN over email for any reason.
 Your SSN is your Primary Account Number for the United States.
(I am unaffiliated, just like this service.)
As in, "Whenever we are sued, we have to undergo Discovery, and they find all those email we really wish had never seen the light of day..."
To put it another way: if you turned around during discovery and told the other party you'd deliberately used a system that caused all your e-mails to self-destruct you could expect to be destroyed in court.