Taking cues from Facebook, Twitter has announced a new DM inbox system which will sort your incoming messages into those from people you follow and those from people you don't, which will go to a new 'Requests' folder.
Of course, this only applies if you've opted to receive direct messages from anyone (which you can do here), but for those who have, it's another way to sort your incoming messages, while, as noted by Twitter's VP of Product Keith Coleman, it also adds another filtering device for safety:
Part of our ongoing efforts to reduce abuse & make Twitter safer, and one that also has many benefits beyond that- Keith Coleman (@kcoleman) May 30, 2017
The change also means that new group conversations you're added to by people you don't follow will also go to the 'Requests' folder - as you may or may not have experienced, every now and then users get added to random group chats by strangers which you then have to opt out of. This alleviates the problem.
Since adding the option to accept all DMs, even from people you don't follow, two years ago, Twitter has recently revised the process to give you the option to accept or delete message threads from strangers, enabling better inbox filtering.
Now, these messages will sit in the separate Requests inbox for you to review whenever you see fit. Once you hit accept, the message will switch to your regular inbox, helping to ensure your message stream remains relevant. Deleting a message from your inbox will delete it entirely, not move it to another folder.
Twitter's been working to update their messaging options for some time. Back in 2015, they removed the 140 character limit on DMs, making it easier to engage and share relevant info, while more recently they've added automated responses and customer service tools to help better facilitate DM interaction between brands and users. Just last week, Twitter released a new ad unit which promotes direct interaction with bots via DM.
With the wider expansion of messaging use more generally, Twitter's moves make sense, and the addition of a new filtering option will further enhance the offering, making it easier to utilize and focus on relevant requests.