I have Xcode version 4.6.1 (on Mountain Lion).
It seems like both my project (I've followed the instruction on how to add MailCore as subproject, and setting build phases) and the example project MessageSender/InboxLister are having the same problem.
The exact error message is
Lexical or Preprocessor Issue
'MailCore/MailCore.h" file not found
Yes, I am building a Mac application.
Make sure that there isn't a space in the path leading up to your project. Libetpan can't handles spaces in the path, so something like "/Users/username/Mail Project/MailCore" won't work because of the space.
actually there is no space. /Users/Daesuk/Documents/Sandbox/Tools/AmazonXTupleLinker/MailCore
I am going to have to say #19 is the only solution for me.