Microsoft has changed how e-mail is routed to Office 365 in order to provide continuing improvements in performance and reliability, and to make e-mail routing more efficient. Now, each custom domain in Office 365 has its own unique Mail Exchange (MX) record value.
Up until recently, MX records for custom domains were “generic”, meaning everyone would point the MX record for their particular domain(s) to a generic MX record such as mail.global.frontbridge.com or something similar, without any reference to the organization. These generic MX records were deprecated on 1 January 2013 and support for these records will end on 1 July 2013. As such, organizations need to update their MX records to domain-specific MX records before July.
Please note that this does not affect P1 user plans, but all E plans.
You can find the specific value(s) for your domain(s) in the domain administration section of your Office 365 tenant admin page. The values are also listed in an e-mail your organization’s technical contact should have received from Microsoft.
Login to the Office 365 portal as an administrator, click on Domains under Management on the left hand side:
Select the domain you want to update the MX records for and click on View DNS settings:
Click on View DNS records:
Scroll down until Exchange Online. In here, look for the Points to address field for MX:
This should be in the format of “company-domain”.mail.eo.outlook.com.
If you do not update all your generic MX records by 1 July 2013, you may not receive a future update, resulting in a mail flow disruption from people outside your organization. Microsoft cannot predict when or if such an update will occur. Even though generic records will be unsupported after this date, Microsoft will e-mail customers if they know of such an update in advance.