设置-隐私-邮件
允许应用获取你的电子邮件 打钩
Looking at the history now I don't think it was the update that fixed it (since the Windows 10 1803 update, I only show a Flash security update and two Defender definition updates).
Instead, after some googling I went to Start/Settings/Privacy/Email, and "Allow apps to access your email" was turned off, so I turned it on. That didn't fix it right away because apparently it requires a restart. That happened after I powered down for the night and restarted in the morning and now it worked. I'm guessing that was what fixed it.
