A few years ago I published a screencast explaining how to put keyboard shortcuts to your email send-from account. With the release of Yosemite, you are going to need to tweak that shortcut. Before, Apple Mail would wrap your email in <arrow brackets>. Now Apple Mail removes the brackets and adds an n dash (Option + "-"). If you've suddenly found your Send-From trick not working, that's why. Go in and reset them with the new syntax and you'll be back in business.