Apple Releases Mail Update for Yosemite
Apple today has released a new version of their troubled Mail app for Yosemite. This version was released to developers as well as public beta testers. This update of Mail for Yosemite fixes an issue that may prevent composing a message.
Developers and beta testers can update to the new version of Mail in the Mac App Store > Updates > Software updates > OS X Yosemite Mail Update.