Starting later today, if you’re using a Yahoo! Mail account in English, French, German, Italian, or Spanish, you’ll be able to access your Dropbox from right inside your inbox. You can add stuff from Dropbox to any email message and save attachments back to Dropbox, too.
This is an amazing feature for Yahoo to implement. The downside is that it does require using the web interface but that’s more an implementation issue than anything else. Saving attachments is great if you use the webmail service when you’re not at your own computer.
This is getting towards what I wrote about a few weeks ago with Mailbox potentially including a way to integrate Dropbox for attachments.