I am getting the error you see in the photo when I import the SKPSMTPMessage library:

The point is that I have no idea what it means. I have done a clean, I have added the files under the Compile Sources, and I have added the CFNetwork framework. Any idea what it means??
It looks like you have the Dropbox SDK included in the app as well, and this uses some of the same files that SKPSMTP uses (for Base64 encoding).
I’m guessing you will need to remove:
from the SMTP folder. If this still does not compile due to duplicate symbol warnings, try removing:
Of course, you should then check that SMTP works OK to ensure the implementation from the Dropbox SDK is compatible.