Exchange mailbox users can access their email from anywhere using the Outlook Web Access (OWA) facility. This may be accessed using any web browser from the following URLs:
Alternatively, you can add a C-NAME entry to your domain’s DNS records to personalise the OWA web address. For instance, you could create a record of ‘owa.yourdomain.com’ or 'webmail.yourdomain.com’ which needs to point to 'owa.messageexchange.com’ in the DNS C-NAME record.
Exchange 2013 users must replace 'messageexchange.com' with 'cloudplatform1.com' e.g. 'owa.cloudplatform1.com'