Just when you thought it was safe to go back into the water because Microsoft had moved swiftly to fix the hybrid connectivity and Exchange 2007 Store interoperability bugs that afflicted Exchange 2013 CU6 since its release on August 26, news comes of yet another problem. The focus that Microsoft had surely hoped would now be on the good news of the increased public folder scalability delivered in CU6 is now firmly back on product quality.
The new bug is the utter inability of an Exchange 2013 CU6 server to be able to proxy Exchange ActiveSync (EAS) connections to a mailbox on an Exchange 2007 SP3 RU13 server. The Exchange 2013 server is unable to process inbound EAS connections and throws an exception in the EAS application pool (within IIS) with HTTP 500 errors (server problems) logged on both Exchange 2013 CU6 and Exchange 2007 servers.
The situation when you discover that a cumulative update doesn't work is complicated by the fact that you cannot remove a cumulative update once it is installed on a server. As TechNet notes: “After you upgrade Exchange 2013 to a newer cumulative update or service pack, you can't uninstall the new version to revert to the previous version. If you uninstall the new version, you remove Exchange from the server.” You could, of course, remove CU6 (and Exchange) from your Exchange 2013 Client Access Servers (CAS - or the preferred multi-role) servers and then reinstall CU5, but that’s a heap of work to fix a problem.
But before we all rush to embrace other solutions, like moving mailboxes off Exchange 2007 to Exchange 2010 or Exchange 2013 servers or reconfiguring namespaces to reroute inbound EAS connections, both of which sound like too much work to me, the good news is that Microsoft has reacted quickly to the problem and has made a patch available (KB2997847) today. You have to contact Microsoft support to get the actual hotfix. To make it easier to maintain servers, the code that you'll get will contain fixes for both Exchange 2007 co-existence issues discovered to date, but if you have already installed the first hotfix, you can simply install this fix over it to get both.
In fact, it's fair to say that the Exchange development group has responded fast as soon as the three CU6 problems have been reported. It's just a pity that they have had the chance to demonstrate how quickly they can fix bugs.
I can’t over-emphasize the need for testing all new cumulative updates before you introduce the new code into your production environment. Yet we still hear reports from people who run into problems when they deploy without testing. On the one hand, I have a certain lack of sympathy in these cases. On the other, I appreciate that some administrators feel under pressure from the cadence imposed by the current Microsoft servicing model for Exchange 2013 and so rush code into production without benefit of testing. In either case, there’s no excuse for the kind of poor quality software that Microsoft has shipped to on-premises customers in CU6.
If you find it difficult to test new software before deploying into production then please take the time to simply do nothing for a couple of weeks following the release of an update to let the other trailblazers find and report any lurking issues. Why rush in where angels (and experienced administrators) fear to tread?
I accept that it is difficult for Microsoft to test a new version of Exchange in such a way that every edge condition is exercised. But the situations that have come to light over the last week are not edge conditions. All of the issues we have seen so far are in well-understood and common areas of functionality that are used by many customers.
Breaking hybrid connectivity with Office 365 is a highly visible problem that undermines the message Microsoft gives to customers that cloud transitions are safe and problem-free. Breaking delegate and mobile access to mailboxes between Exchange 2007 and Exchange 2013 doesn’t create a feeling that interoperability with new versions will be a happy event in the future and might influence the willingness of customers to move to Exchange 2016 when it appears next year. All in all, CU6 is now officially a perfect mess.
Please Microsoft – pretty please even – can we have a version of Exchange 2013 that doesn’t contain such an array of irritating bugs? It would be nice. Very nice.
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