I have a problem with the handoff feature on my iPhone 6s (iOS10): handoff between the Mac and the iPhone does not work when composing emails. For example, if I start writing an email on my Mac and try to handoff to the iPhone, the iPhone shows the following message: "Failed to continue activity. Handoff could not be completed." The handoff feature works fine when simply viewing emails. It also works fine with Safari. I'm pretty sure that the problem is with the iPhone, as the handoff feature works just fine between my Mac and my iPad, but not between the iPhone and the iPad. Basically, it fails only with the iPhone.