Spell-check doesn't work on words with dashes (Mail.app in Yosemite)
This is not a answer...but to show the result of a test

It confirms a problem with using a dash with spell checker in Mail.app and Notes ect... on my MBA with 10.9.5



The result is sporadic, sometimes if the word before dash is correct it will ignore the word after dash, sometimes not.

Interestingly if I enable check Grammar with Spelling it will work correctly.