Many companies use the Google DNS servers (18.104.22.168 and 22.214.171.124) as forwarders to resolve internet addresses.
Whilst performing some exhaustive troubleshooting on Office365 & Outlook slowness & connection issues, we have uncovered incorrect addresses being resolved for EMEA customers.
When using Office365 in EMEA, outlook.office365.com is a CNAME record that should always resolve to either emea-east.outlook.com, or emea-west.outlook.com. This means you access the servers closest to you, and don’t cross the Atlantic multiple times to get to your data.
I have seen multiple occurrences recently of Google’s servers resolving UK based clients to outlook-namwest.office365.com which causes mail opening times of between 3-8 seconds (depending on the message size) and a raft of other connection and disconnection issues.
I recommend not using Google’s name servers if you’re either using Office365 or rely on accurate name resolution, but either OpenDNS or the servers provided by your ISP.
I’ll shortly post a powershell script in the downloads section that will send an email if any of your nameservers return a non-emea result.