When I search All Mail in Outlook, any emails in the results (ordered by Date Sent) that are in the Sent folder, appear without their dates, so theye are listed at the end of the Results, below all the others from other folders which do have their dates and are therefore listed in the correct Date Sent order. 

If, however, I search the Sent folder only, the Sent emails that come up in the results DO have their dates; it's just when searching All Mail that their dates disappear. 

I'm sure this didn't used to happen.  Could a bug have been introduced in a recent update?