I've used this in the past but came away disappointed as it regularly breaks over attachment sizes. I was using it to store my website backups in dropbox.
Instead of this, now I setup a simple python dropbox script on my webserver which allows me to do few good things:
1. No connecting to third party apps.
2. No need to go through email servers, I can directly store the backups to dropbox
3. I still added an email addon layer on it for other usage where I send the files to my own mail server and the script then puts them into dropbox.