I get this:

$ ping outlook.office365.com
PING outlook-namwest.office365.com ( 56(84) bytes of data.
64 bytes from icmp_seq=1 ttl=242 time=17.6 ms

$ wget http://outlook.office365.com
--2016-04-20 17:27:33--  http://outlook.office365.com/
Resolving outlook.office365.com (outlook.office365.com)... failed: Name or service not known.
wget: unable to resolve host address ‘outlook.office365.com’

Note that wget says "unable to resolve" not "can't connect".

It is only for that host. Any other website works.

wget also works.

Loading http://outlook.office365.com in Firefox also fails.

What is going on and how do I fix it?

Platform: Ubuntu 14.04 LTS, x86-64. No recent config changes or software updates that I am aware of. This stopped working today (was ok yesterday).

  • What does the hosts: line in your /etc/nsswitch.conf look like? – 84104 Apr 21 '16 at 1:03
  • @84104: I have hosts: files mdns4_minimal [NOTFOUND=return] dns. File mod date a year ago. – Alex I Apr 21 '16 at 1:11

I think there is a problem with IPv6. If the result of host -t aaaa outlook.office365.com is "failed: connection refused.", please try wget -4 http://outlook.office365.com/.

  • Spot on! That works. Now: how do I disable IPv6 temporarily on my system? – Alex I Apr 21 '16 at 2:33
  • Also, why does the resolve fail for IPv6 only? I can see how connectivity may fail in a v6 only way, but not necessarily how resolve would fail in a v6 only way. – Alex I Apr 21 '16 at 2:34
  • 1
    I think, your DNS Server does not support IPv6. host -t aaaa outlook.office365.com (Query to Google's DNS Server) => correct result. – Taichi Yanagiya Apr 21 '16 at 2:42

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