Throw the Switch and Direct All Traffic to Office 365
After you have migrated both e-mail and portal data, you are ready to throw the switch and direct all traffic to the new Office 365 environment. Throwing the switch is accomplished by updating your Domain Name System (DNS) records in your domain registrar. The results of this simple procedure are enormous. After you update DNS, every user of your current system is directed to the Office 365 system.
A DNS record is a translator from human readable computer names to computer readable computer names. For example, if you type www.microsoft.com into your web browser, the Microsoft web page appears. How does this happen? Your computer sees microsoft.com and knows it is a text entry.
Computers talk to other computers by using numbers known as Internet Protocol (IP) addresses. Your computer needs to find out the IP address of the computer running the microsoft.com website. It does this by querying a DNS server. The DNS server looks up the text-based address (known as a domain name) and sends back the IP address. Your computer can now use the IP address to contact the Microsoft computer.
When you update the DNS records for the e-mail, for example, you are telling the DNS lookup system that when someone wants to send you an e-mail, their computer should use the IP address of Office 365 rather than the one you were using before. In essence, after you update DNS you have thrown the switch and are using Office 365rather than the old system.