Microsoft has had been planning to drop Windows Live Messenger in favour of Skype for quite some time now. See:
 - http://www.bbc.com/news/technology-20222998
 - http://arstechnica.com/information-technology/2013/01/microsoft-messenger-service-not-going-anywhere-just-yet/

Even though the close down was initially supposed to happen on 15th March 2013, the XMPP gateway that is used by the Windows Live provider continued to work. But not anymore. I can not connect to it, and neither can others (see bug 727905), and they have removed the SRV record for _xmpp-client._tcp.live.com.

rishi@kolache ~$ dig SRV _xmpp-client._tcp.live.com

; <<>> DiG 9.9.4-P2-RedHat-9.9.4-12.P2.fc20 <<>> SRV _xmpp-client._tcp.live.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 48773
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;_xmpp-client._tcp.live.com.	IN	SRV

;; ANSWER SECTION:
_xmpp-client._tcp.live.com. 396	IN	CNAME	rds.live.com.nsatc.net.

;; AUTHORITY SECTION:
nsatc.net.		813	IN	SOA	admin.nsatc.net. fixme.example.com. 1397609172 10800 2700 3600000 900

;; Query time: 37 msec
;; SERVER: 10.38.5.26#53(10.38.5.26)
;; WHEN: Wed Apr 23 14:31:04 CEST 2014
;; MSG SIZE  rcvd: 147

rishi@kolache ~$