Out of office does not trigger fact check received

https://www.pivotaltracker.com/story/show/66656546

PR investigation references:
Out of Office headers thread for Outlook/Exchange Server: http://stackoverflow.com/questions/1027395/detecting-outlook-autoreply-out-of-office-emails

The problem with a lot of  Fact Check emails is that they don't have any relevant headers set, so checking the subject is also used. Only when the subject starts with (case insensitive) 'out of office'.

For google/gmail headers, I set one of my accounts to on vacation and checked what headers were set, along with the values.