What is Autodiscover service, and how it works?
The Autodiscover service in Microsoft Office 365 is an exchange feature which helps in configuring the user’s mailbox automatically. It is used for minimizing the user configuration and deployment steps by providing access to Exchange features for clients.
To make Autodiscover work without any user interaction, Microsoft has developed a method for telling Outlook to find the configuration info it needed automatically. This was accomplished by using a few DNS lookups based on a set piece of information that everyone had to put in, i.e., the email address.