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Microsoft Releases Flawed Cumulative Update 6 for Exchange 2013

• By Kurt Mackie
• 09/02/2014

Microsoft released Cumulative Update 6 (CU6) for Exchange Server 2013 late last month, but it isn't problem free, especially for organizations with hybrid deployments to maintain.

Problems are being reported by Microsoft most valuable professionals (MVPs), with Microsoft responding fairly quickly in some cases. Jeff Guillet, an Exchange MVP, pointed to a problem in using the Exchange Admin Center after applying CU6 in hybrid scenarios. A "hybrid" scenario means deploying Exchange Server 2013 on premises alongside using a public cloud e-mail service, such as the Exchange Online service of Office 365.

Guillet flat out recommended that hybrid Exchange users should not install Exchange Server 2013 CU6, noting that it isn't possible to roll back to a previous state after doing so.

With CU6 installed, the Exchange Admin Center doesn't work when trying to create new mailboxes in the Office 365 service. In addition, mailboxes can't be moved to Office 365 after applying CU6. It's also not possible to "create In-Place Archive mailboxes" with CU6 installed, Guillet explained in an Aug. 29 blog post.

Microsoft issued a script on Sept. 1 to address these Exchange Admin Center problems after applying CU6. The script, available at this support page, is designed to be run on systems with this particular problem. However, the script assumes that Exchange is installed on the same logical drive as Windows, according to a WindowsITPro article by Microsoft Exchange MVP Tony Redmond. An improved version of the script that checks for the Exchange installation path is available from this TechNet gallery page, Redmond noted. This improved version of the script was devised by Microsoft MVP Michel de Rooij, who explains its nuances at this page.

Microsoft also noted that Exchange Server 2013 users could experience a database failover problem with CU6 installed. The problem only happens when Exchange Server 2013 coexists with Exchange Server 2007, according to a Microsoft support article:

When the updated server that is running Exchange Server 2013 tries to authenticate the user, it uses a mechanism that is not understood by Exchange Server 2007. This causes the Exchange Server 2013 Store process to crash and fail over the database to a different server. Co-existence with Microsoft Exchange Server 2010 is not affected by this problem.

Microsoft's support article points to a hotfix that's available to address this database failover problem. However, affected organizations still have to contact Microsoft Customer Support Services to get it as the hotfix is not available online.

CU6 fixes a number of bugs, including the Hybrid Configuration Wizard error problem from Cumulative Update 5. It also notably expands the public folder hierarchy limits in Exchange Server 2013 to 100,000 folders. A problem in which unauthorized users were able to send messages to public folders regardless of their permission status is also addressed by CU6. Microsoft explains those details in this blog post, adding that the public folder hierarchy expansion represents its "first round of investments" along those lines. Additionally, it plans to issue public folder deployment guidance "in the next few weeks."

Even if IT pros weren't impressed by the improvements wrought by CU6, if they are running a hybrid environment with Exchange Online, they are still required by Microsoft to keep current with Microsoft's cumulative update releases. As Redmond explained, the idea of staying current with cumulative updates is to keep the premises-based product as current as possible with the hosted service, but the quality issues of late associated with Microsoft's Exchange Server update releases may cause IT pros some degree of despair, he noted.

Other MVPs also are scratching their heads over the quality issues in conjunction with the increased release pace. Exchange Server cumulative updates are issued quarterly now.

Microsoft MVP Michael Van Horenbeeck suggested in a blog post that maybe organizations with hybrid Exchange environments should just stick with Cumulative Update 4 for now. He described CU4 as the last nonproblematic release for those environments:

On a final note, I'm wondering what customers with a hybrid deployment should do. According to Microsoft support guidelines, hybrid customers are requested to stay current with Exchange Server updates. But given that this is now two consecutive update[s] that are causing problems, one might start to wonder if it's not better to stay at CU4 as it was the last CU which did not have any hybrid issues…

In any case, Microsoft expects IT pros to test its update releases before adding them to a production environment, while keeping current with the quarterly release pace. Meanwhile, MVPs are wondering why so many updates seem to slip out with problems.

Update: Microsoft noted a second coexistence problem between Exchange Server 2013 CU6 and Exchange Server 2007 on September 8. This second problem concerns a glitch with routing Exchange ActiveSync traffic to Exchange Server 2007 mailboxes after applying the update. The company issued a Knowledge Base article with a workaround suggestion here, although a note by Brent Alinger of Microsoft at the end of this blog post indicates that a hotfix for the problem can be obtained by contacting Microsoft. There's also a problem with Outlook Web App not producing a new mail sound notification, which Microsoft is working on, according to Alinger.