Office 365 DNS for Success!
Robert Dick, Office 365 MVP
Senior Consultant, itgroove
Who am i?
30+ years in IT, more than half in Consulting
Microsoft Office 365 MVP (one of 4 in Canada)
MCP, MCTS, VMSP, VMTSP
SMB Team Lead, Senior Consultant with itgroove
DNS: OK, what is it?
The “dry” definition:
DNS is an abbreviation for Domain Name System, a system for naming computers and network services that is
organized into a hierarchy of domains. DNS naming is used in TCP/IP networks, such as the Internet, to locate
computers and services through user-friendly names.
DNS defined: Domain Name System(DNS) - TechNet
A little more friendly …
“Yellow Pages”, “Phone Book” or 411 for the Internet!
Maps IP addresses to textual information that we mere humans can read and understand (and systems
Multiple record types (types of text) to facilitate different tasks and functions
Some simple, some not so much …
Some Standard DNS Record Types
NS – Name Server resource record: points to the authoritative nameservers for your domain
A – Address resource record: maps address 18.104.22.168 to name www.itgroove.net (lookup is name)
PTR – Pointer resource record: reverse of A record, maps name to address (lookup is address)
CNAME – Canonical name resource record: maps one name to another
MX – Mail Exchange resource record: maps IP, name and “weighted preference” for your email server(s)
SPF – Sender Policy Framework record: positively identifies authorized email senders for your domain
SRV – Service Resource record: relatively new type of record that maps for specialized services (like Lync)
Where does your DNS live?
External DNS lives at your Domain Registrar or your designated DNS provider, this is what everyone on
the Internet “sees” (Your external domain is .com, .net, .org …)
Internal DNS lives on your internal DNS servers – normally your Domain Controllers in the Windows
world (Your internal domain could be .local or something different from your external)
Both need to reference all of the required DNS records in order for your Office 365 to function
correctly on your internal network as well as on the Internet
This probably means you will need “split brain” DNS entries in your internal DNS system (your internal
DNS has records for both your internal domain as well as your external domain)
What DNS is critical to your Office 365 migration?
Microsoft defines the following as fundamental to bringing your O365 tenancy online:
msoid CNAME record pointing to a specified Microsoft DNS record for authentication
@ or yourdomainname.com TXT record used to verify ownership of your domain
autodiscover CNAME record pointing to autodiscover.outlook.com
<Mxtoken>.mail.protection.outlook.com MX record that points to the O365 mail servers
v=spf1 include:spf.protection.outlook.com –all SPF record
_sipfederationtls, _sip SRV records required for Lync operation
sip, lyncdiscover CNAME records required for Lync operation
Some “real world” examples (register.com)
What’s Easy? What’s Not??
CNAME, TXT, SPF and MX are all relatively easy records to create yourself
SRV records are more complex, vendor UI’s may not allow you to easily enter the required information,
be prepared to make multiple tries
Some third party suppliers don’t have the backend to support the SRV records (some of the ISP’s are in
If you can’t make the changes easily yourself you should be looking at another DNS provider!
Microsoft lists a number of providers that work well with O365. Previous example of register.com
shows a “clean” SRV record entry.
DNS entries all made! Now what?
Use the “test” button inside O365 to test DNS entries.
If all good O365 will “light up” your tenancy and you are good to go!
If not all good, O365 will highlight the DNS entries that are problematic so you can go back for another
kick at the can.
Go through the loop until you are all good and tenancy is live!