Office 365 Data Center and Exchange CAS endpoints

Worldwide Office 365 Data Centers and Exchange CAS endpoints One of the main things you need to get right to ensure the most efficient and speedy connectivity to Office 365 is where in the world your DNS call is being completed from. You'd think this wouldn't matter, you do a DNS lookup for your Office 365 tenant, get the address, then connect right? Well, normally yes, but with Office 365, especially with Outlook, Microsoft does some pretty clever work to utilize a worldwide array of data-centers to help ensure you get connected to a regional data-center. Your Outlook connection will do a DNS lookup and Microsoft will use the GEO location of that lookup to connect you to your 'nearest' Microsoft Data-center IP Address. Outlook will connect to a CAS server based on the DNS query and use Microsoft's fast Data-center to data-center backbone network to connect you to the data-center where your Exchange mailbox data is located. Generally, this works well, however, you may not always under all circumstances be connected to the closest data-center. Using the picture below, consider a case in an enterprise where users that will use Office365 are located in Dallas TX (BLUE), and an Office365 Tenant has been setup for them in the San Antonio data center (PURPLE). However, all traffic external to the organization goes from Dallas to Phoenix (RED), on a private connection, before reaching the Internet. Users in Dallas, when doing DNS lookups for hosts on the Internet end up using DNS servers in Phoenix (because that is where data leaves the company network). Users in Dallas will receive IP addresses of the nearest Office365 data center as San Jose (ORANGE). From there, the data travels all the way back to San Antonio (PURPLE) where the Tenant is hosted. If the internal DNS servers are not adjusted to point “outlook.office365.com” to the San Antonio data center (PURPLE), users will have a horrible experience due to the many network hops and latency in between. Changing the DNS servers will cause Dallas users to jump directly to the truly “nearest” Office365 data center. The change in local DNS would only need to be a CNAME record pointing to outlook-namcentral.office365.com (at the time of this posting…it may change in the future). Unexpected Office365 network routing Below is a report, run hourly from our servers, that query's 1000's of DNS servers all around the world and locates all available Geographic Exchange Online CAS Server endpoints for outlook.office365.com. You can use this data to make sure you are connected to the fastest Office 365 CAS servers for your particular environment. To see which data center by default you are receiving from your DNS query you can simply ping outlook.office365.com. From our Phoenix office we receive the following GEO assignment to outlook-namnorthwest2, however, latency and speed testing shows that the best data center for our Phoenix office at the time of posting this blog would actually be outlook-namnorthwest. It's clear that Office 365 customers need to understand how end users are being routed and preform the proper due diligence to make sure end users get the optimal experience from the cloud. All data and information provided on this site is for informational purposes only. www.priasoft.com makes no representations as to accuracy, completeness, currentness, suitability, or validity of any information on this site and will not be liable for any errors, omissions, or delays in this information or any losses, injuries, or damages arising from its display or use. All information is provided on an as-is basis. Featured Migration Products Exchange Public Folder Analyzer Gain control and deep insights into your Exchange / Office 365 Public Folders with comprehensive reporting, analysis, and remediation. Public Folder Migration and Synchronization Manager Say goodbye to unreliable third-party tools. Our solution ensures seamless mail-enabled public folder migration, content transfer, and precise permission preservation. Super-ExMerge for Office 365 and Exchange Your DevOps-friendly solution for managing PSTs, from ingestion to data export for legal discovery, and efficient Exchange task management, all powered by PowerShell. Profile Update Manager for Outlook Ensure smooth transitions during migrations with our Outlook Profile Update Manager. Don't let AutoDiscover issues ruin your experience—update profiles correctly from the start.