It’s now possible to use your Google account, Facebook account, or your Microsoft account to log in to Bing Webmaster Tools. This will make it easier for webmasters to log into your toolset.
This is what it looks like when you try logging in:
According to Microsoft, this “means that the messages Webmaster Tools may occasionally send you about your managed properties will be sent to the email account associated with the webmaster tools account you are logged in with. The most recent messages will still be available in your Webmaster Tools Message Center.”
This should be available as a login option for all users who verified their websites with Bing Webmaster Tools at bing.com/toolbox/webmaster.