Twitter has made it possible for any user to send  a direct message to any other user, the company announced in a blog post Monday.

Under the old settings, users could only direct-message those who followed them -- which sometimes meant that you had to ask people to follow you in order to send them a personal message. Now, those days are over, if you so choose.

The change is opt-in, meaning that you don't have to open your mailbox to the public if you don't want to --  and that you can turn it off if you don't like it. Twitter now also allows users to reply to anyone who sends them a direct message, regardless of who follows whom.

If you want to turn on the feature, you can head to your settings page and select the "Receive Direct  Messages from anyone" option.  Once you do that, a new messaging button will appear on your mobile profile pages.  (To send a message from the Web, users should still go to the "Messages" tab and hit "New Message.")

Why, you may ask, would anyone do this in an age of online harassment and information overload?

Twitter makes the case that if would be useful for businesses to field compliments or complaints from their customers without having to follow each of them individually. From a certain point of view, that makes sense: the company has been under pressure lately to up growth, revenue and engagement on its social network. Catering to businesses, and giving them an easy way to interact with customers, is a way to accomplish all those goals.

Twitter had previously rolled out a test that allowed some users to receive messages from anyone, before rolling it back around a month later, as The Next Web reported. Some of those early users have kept the feature on because they found it useful. Customer service accounts, for example, often use the direct message feature a lot to get information to resolve problems, as do journalists who want the option to receive tips from anyone on the social network.

But the feature can also increase the chances for spam or abuse. Twitter, after all, is in an ongoing fight to curb harassment on the site -- particularly against women and other minority users -- to make it a safer place for all users and for legitimate businesses. There are many well-documented instances in which spammers and trolls have publicly harassed others over Twitter; this could give them another, more personal, avenue for that abuse.

Twitter has introduced anti-harassment filters and other tools aimed at making it easier for users to screen out and report bad behavior. But the firm has also been clear that it doesn't want to introduce features that make it difficult for people to express their views.

"We must make sure it's not so easy to engage in abuse, but also not cross the line to make it so that you can't post any content," Del Harvey, Twitter's head of trust and safety told The Post last year. 

To address those issues with this new feature, company said on its help page that users who've enabled this feature can block the sender to stop receiving messages. Obviously, this won't prevent that sender from creating a new account and sending more messages -- a common trolling and spamming tactic -- but it's a start.  Twitter also limits the number of direct messages anyone can send per day to 1,000 messages, and reserves the right to suspend an account temporarily if someone sends identical messages to multiple accounts in a short period of time.

Basically, if you turn the option on, you should be aware that it comes with its own set of risks.  And if you're at all uneasy about getting unsolicited personal messages -- and don't have any need to do so --  it's probably best to keep the feature turned off.