Feb 20, 2015

In today’s blog I will talk about planning for Exchange online and discuss the correct DNS configurations required for a successful coexistence or migration. Before you start migration or coexistence, you need to analyse your organisations environment.  There are various factors that you should analyse. Mailbox size: You should plan for reduction on the premise of your mailbox size. It is one of the major factors that define the time it will take to migrate to Exchange Online. Internet speed: Controls the duration of migration. DNS configuration: You need to plan and create the required MX, CNAMES and Autodiscover records well in advance. Apart from these core factors, you should also plan for efficient retention, journal entry and archiving. The exchange online service uses several records Autodiscover CNAME records for client Autodiscovery, and a Sender Policy framework (TXT) record for anti-spam protection. In a hybrid environment, where organisations have both exchange servers on cloud and on premise, two TXT records are needed; one record is for the exchange delegation and the other one is for the domain name. A MX record is required for mail federation between the servers. In a hybrid deployment, you need to consider incoming email routing, as incoming emails can route via office 365 or through on premise infrastructure. Specific DNS records must also be configured for such operations, and the same applies to outgoing mail routing as messages can be routed directly to the recipient of through an Onpremises deployment. Finally, a single sign on implementation, an 'A record' is needed to publish the active directory federation server address. Before you make changes to your domain, plan and document your changes properly.