[h2s]

Worth bearing in mind that this is effectively DRM for email, with all the negative connotations that DRM brings.

[teacup50]

It's already bad enough that people put dropbox links in their e-mails, negating the value of long-term e-mail archiving.

It's extremely useful to be able to go back in time and have full conversation history, including associated resources.

[chimeracoder]

While I agree with this, I find it equally annoying when people send 3MB attachments as emails (and then keep resending them for every email in the conversation!).

It would be nice if a Dropbox link included a hash of the file, functioning more as a magnet link than a URL (emphasis on the "L - Locator" in "URL").