This is a quick public service announcement before the weekend starts. Exchange Online Protection has been allocated a new IP range. Starting in 30 days, EOP will add 220.127.116.11/16 to the IP pool that is used to deliver mail that passes through custom connectors (ex. EOP outbound connector which routes inbound mail to your on-premises environment). If you have mailboxes located on-premises and lock down your environment to only accept mail from EOP, you will need to add this new range to your firewall exception list.
Please see Exchange Online Protection IP addresses for the complete list of IPs. Note that this list only contains IP address ranges that are used to relay mail through custom connectors.
We do publish an RSS feed that we update when any Office 365 URL or IP range changes. By subscribing to this feed, http://onlinehelp.microsoft.com/en-us/office365-enterprises/o365ip.rss.xml, you’ll be notified of all Office 365 IP changes as soon as they have been announced. For more information, see Office 365 URLs and IP address ranges.
Have a great weekend and happy first day of spring!