Last week we and the community were surprised by an update for Outlook 2010 and Outlook 2013. These updates ( and ) broke our advanced collaboration features.
Normally Outlook 2010 and Outlook 2013 receive an update on Patch Tuesday, which used to be on the second Tuesday of each month.
Microsoft made the following announcement on this;

In this article, Microsoft basically outlined that they will decouple the security updates from the normal updates. Office users can expect non-security updates on the first Tuesday of the month, while security updates can be released on the second Tuesday of the month.
This change only applies to the OEM versions of Outlook, not the Click-to-run versions.

With this additional Patch Tuesday, the chance that the advanced collaboration features breaks increases, but over time the built-in auto-patcher has been better and better at automatically patching the new updates from Microsoft. For example, we have already been enjoying the results from the work of auto-patcher for the second Patch Tuesday.
Since April 2016 is the first month of this change, we will monitor the next updates from Microsoft to offer our users the best experience and keep you updated on issues and resolutions.