Earlier this month was a big day for Exchange updates. Not only did we get Cumulative Update 12 for Exchange 2013, but we also got our first update for Exchange 2016. Yay!
As always, test these updates in a lab first! I recommend checking out this 7-part guide on configuring Exchange in your lab. It doesn’t take much to get one going.
The updates are as follows:

Exchange Server 2016 Cumulative Update 1 | UM Language Pack Download

Exchange Server 2013 Cumulative Update 12 | UM Language Pack Download

Exchange Server 2010 SP3 Update Rollup 13

Exchange Server 2007 SP3 Update Rollup 19
So what’s new?
This update is a culmination of bug fixes and feature tweaks. Most notably the OWA S/MIME control ditches its SHA-1 signing certificate in favor of the more secure and robust SHA-2. This signing change makes it to all supported versions of Exchange. For 2007, which is in extended support, this is the only thing Rollup 19 addresses. Exchange 2010, also in extended support, similarly sees this update and just one other minor tweak–which is the introduction of a link to the new Hybrid Configuration Wizard.
Despite the inclusion of this link in EMC, the new Hybrid Configuration Wizard was able to run against prior roll-ups of Exchange 2010. This update simply adds a link for ease of access. Be sure to check out this blog post from the Exchange Team for more info on the new HCW for Exchange 2010.
Another cool update, that flew under the radar, is that the web.config file for Outlook on the Web will now be preserved during a cumulative update. This is neat because it will preserve any customization admins may have made to that file. Sadly this change only applies to Exchange 2016 deployments but let us keep our fingers crossed this will be ported back to Exchange 2013.
One surprising plot twist was the retraction of Mailbox Anchoring in the Exchange Management Shell. This had been implemented in the previous 2013 update and was set to ship with 2016 CU1. Exchange CU12 sees this change reverted and 2016 never sees it at all.
Mailbox Anchoring was the concept of making sure that an admin was always getting the same experience when connecting to the Exchange Management Shell. This was especially important in an environment where Exchange 2013 and 2016 are load balanced in the same pool.
In essence, when you opened Exchange Management Shell mailbox anchoring would always proxy you to the server that hosted your admin mailbox. If your admin account didn’t have a mailbox, or, it was unavailable, then it would proxy you to a server hosting the arbitration mailbox. If neither were available then the Exchange Management Shell would fail to connect. At this point, your only option was to connect through local PowerShell and add the Exchange snap-in.
Microsoft has reverted this change in response to community feedback.
As mentioned in a previous post .NET 4.6.1 continues to remain unsupported. The Exchange Team has indicated that support will be added in a future cumulative update. For now, keep that update away from your Exchange servers. As of writing 4.5.2 remains the highest supported version for Exchange 2013 & 2016.
Other items of note include:
- Exchange 2016 receives 17 new languages in Outlook on the Web.
- Exchange 2016 ditches self-extracting packages in favor of ISOs for delivery.
- Workaround for .Net update KB3097966 causing significant slowdowns in Exchange installations is documented here.
- Lag Replay Manager is enabled by default in 2016 CU1 (but can be disabled).
Schema Updates Needed
Exchange 2016 Cumulative Update 1 includes schema updates. You can apply these beforehand by running SETUP /PrepareSchema from the command line. The graphical setup will also perform this step if it detects the schema has not been extended.
Running this beforehand is critical in environments where the Exchange admin may not necessarily be the Active Directory admin, or, the Exchange Admin does not have the rights to extend Active Directory. You will also want to run SETUP /PrepareAD to get the latest RBAC definitions.
If upgrading from Exchange 2013 Cumulative Update 7-11 to Cumulative Update 12, then there are no schema changes. However, if migrating from an earlier update you will need to perform a schema update.
Note: While Cumulative Update 12 does not include updates to the Active Directory Schema, it does include additional RBAC definitions requiring SETUP /PrepareAD to be executed.
Microsoft documents the schema update process here.
For a quick reference on schema and build versions check here.
Any insight into future Cumulative Updates?
We had hoped that the ability to rebuild indexes from passive copies would make it into CU1. Looks like we will have to wait a little longer. Fingers crossed this enhancement will make it to CU2. More info on that upcoming feature in Greg’s video below.
As mentioned earlier it is also likely we will see support for .Net Framework 4.6.1 in the next batch of Exchange updates.
Required for hybrid
Microsoft requires that anyone in a hybrid environment be on the latest cumulative update.
Other important news
For those that haven’t seen it, the Exchange Team posted an important notice about hybrid mail flow back in February.
Simply put, this potentially affects hybrid mail flow between an on-premises Exchange 2013 environment and Office 365. Regular mail flow or encrypted mail flow is not affected. Exchange 2010 and 2016 is not affected by this.
If you are still on Exchange 2013 CU8 or lower, or, you have upgraded to CU9 (or later) and not rerun the hybrid configuration wizard you will need to take the action listed in the link before April 15th.

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