Microsoft's Windows Live Messenger will be switched off in China in October, marking a final end to the 15-year-old service.
Originally known as MSN Messenger, it was launched in 1999 but was switched off for most users in 2013, after Microsoft bought rival Skype.
Users in China continued to use the old service but will now be transferred to Skype by 31 October.
Windows Live still had as many as 330 million users as recently as 2009.
But those numbers later declined, while users of Skype rose to nearly 300 million by 2012.
The service came to China in 2005, but later faced stiff competition from domestic rivals such as QQ messenger, built by Chinese firm Tencent.
A number of Chinese Windows Live users received emails from Microsoft on Thursday, Chinese newspapers reported, informing them of the planned closure.
The emails told users they would get free Skype credit when they migrated over to the new service, the newspaper said.
MSN Messenger began as a simple text chat service in 1999, a rival to AOL's AIM service and ICQ.
It later added features such as photo delivery, video calls and games as the technology developed.
But Microsoft's purchase of Skype for $8.5bn (£5.1bn) in 2012 spelled the beginning of the end for the service.
MSN Messenger was a hard-working internet visionary which taught a generation to touch-type and lol, writes BBC technology reporter Dave Lee.
It touched the lives of millions of teenagers who, in an age before real social networking, were just getting accustomed to what it was like to live on the internet.
MSN Messenger heralded a new era: a time when chatting up a classmate no longer meant the terrifying prospect of actually having to say something to them.
It meant no longer would young teens have to endure the torture of ringing the landline number of their newest crush - knowing there was a high probability that dad would pick up.
But after all the "ASL?"s and "u there?"s, Messenger's loyal subjects became less dependent. "I'll brb", people said... but they never did.
Other sites, smarter and better looking, would see Messenger cast aside. In an age of exciting digital discovery, Messenger became the web's wooden toy.
After a long career, it spent its final year enjoying a comfortable retirement in China. Its less well-regarded relative, Windows Messenger, still battles on on work computers the world over.
"It's like MSN," office workers say, "…just not as fun."
MSN Messenger is survived by Facebook, MySpace, Twitter, Snapchat, Skype, Google+ and Instagram.