Twitter has announced plans to change how direct messages work on the social network, with a new feature enabling users to be privately messaged by anyone also using the service. Previously, the system only let private, one-to-one messages be sent between users who were mutually following each other.

The original system was put in place to cut down on both spam and harassment, but Twitter is changing that, enabling users to message each other in private without that initially expression of interest.

Twitter has tested this feature before in 2013, when it was removed quickly. However, users who tested it at the time lost the option to switch off the feature, and can still be privately messaged by anyone to this day.

This time, the feature will be opt-in, rather than automatic, and users will be able to opt-out from it ay any time. Twitter seems to intend the change to primarily enable individual users to have private conversations with brands and businesses.

“Previously, if you wanted to send a Direct Message to the ice cream shop down the street about how much you love their salted caramel flavour, youd have to ask them to follow you first,” wrote Nhu Vuong, senior software engineer for Twitter in the blog post detailing the changes. “With todays changes, the ice cream shop can opt to receive Direct Messages from anyone, so you can privately send you appreciation for the salted caramel without any barriers.”

“The move from Twitter to allow anyone to contact a user via direct message is an interesting one, particularly for marketers and retailers,” said John Fleming, marketing director for EMEA & APAC at Webtrends. “The opt-in feature will allow brands to directly engage with consumers from both a marketing and a customer service angle, giving companies a new channel from which to identify and target users.

“However, it is imperative companies dont abuse this feature for communication, turning it into the new send-all marketing email. It has to be relevant. As consumers, were happy to sign up to receive updates from brands, but only both to open the ones we find relevant. Companies sending blanket messages to all contacts are wasting large chunks of their marketing budget.”

Despite the feature being opt-in, many Twitter users have reacted negatively to the news, claiming that it will encourage harassment. Twitter CEO Dick Costolo admitted earlier this year that the platform has problems with online harassment, and needs to address the tactics it uses to curb abusive behaviour.