Why Exchange 2016 ignores Outlook 2007

Part of planning a deployment of a new on-premises release of Exchange is a review of client requirements. It’s therefore reasonable that anyone who is interested in deploying Exchange 2016 might start to look at clients to make sure that users will be able to access the new server after it is deployed. It’s also true that you might be interested in new clients if you want to deploy technology that’s only available in a specific client. Modern or multi-factor authentication is a good example as Outlook 2016 offers more options than available in earlier versions (and especially so if you use Office 365).

Returning to the topic in hand, TechNet lists the client requirements for Exchange 2016 as

Exchange 2016 supports the same set of Outlook clients as Exchange Online does, which is how it should be. It wouldn’t make sense for the latest version of the on-premises server to support a different set of desktop clients. Remember, if you run a hybrid deployment, you’re forced to keep up to date with the latest updates as Microsoft releases them for the on-premises versions, so this is just another twist of the “newer is better” story.

Curiously, TechNet doesn’t mention ActiveSync clients or browsers, but hey, you can’t have everything on one page. For those who are interested, the set of supported browsers is the same as for Exchange Online. That page is incomplete too because it doesn’t cover the Edge browser. Then again, the Edge/Office 365 combination wasn’t great in the early days. It seems to have settled down in the Threshold 2 release of Windows 10.

As for ActiveSync, although Exchange 2016 uses ActiveSync version 16, it really shouldn’t make much different to your clients as the ActiveSync protocol is less demanding in terms of version compatibility than the fatter clients are.

Returning to Outlook, the lack of support in Exchange 2016 for Outlook 2007 might come as a surprise for some. However, it’s a fact of computer life that age and functionality pass software by over time. In other words, software vendors like to match up new versions of server and client because they know that some features are designed to only work when the two are used together.

Modern attachments provide a great example. This feature allows you to attach links to documents held is SharePoint or OneDrive (if you use Office 365) sites instead of the traditional method of sending copies of files around. Working alongside Exchange 2016 and with SharePoint configured correctly, Outlook 2016 knows how to perform this trick, but earlier versions remain in blissful ignorance of the wonders of modern attachments. Of course, it takes more than a new client to make old users change the habits of a lifetime, so I have my doubts that modern attachments will be embraced by the masses, but that’s another day’s story.

It’s always been the case that new versions of Outlook have exposed new server functionality. For instance, Outlook 2010 brought MailTips to the party while Outlook 2013 enabled Data Loss Prevention checking and site mailboxes.

And each new version of Exchange has caused grief to planners who suddenly realized that they had to upgrade desktop clients too. Probably the biggest outcry in recent times was caused by the removal of UDP support in Exchange 2010 as this affected the ability of Outlook 2003 clients to connect to that server. Microsoft brought back UDP in Exchange 2010 SP1 RU3 to soothe the concerns of the customer base, but other issues meant that Outlook 2003 was never a great client for Exchange 2010.

As Microsoft points out in their blog post “Outlook 2016: What Exchange Admins need to know”, new clients can take a dim view of old servers too. In this case, Outlook 2016 won’t connect to Exchange 2007 and the case advanced in the post is that “Outlook 2016 does not connect to Exchange 2007, as Outlook 2016 requires technology (e.g. sync, search, auto-discover) present in Exchange 2010+.”

However, the features cited as examples are a curious set. For instance, both search and synchronization are supported in Exchange 2007 – but in a different way, which I guess is the point. In addition, Autodiscover was introduced in Exchange 2007, so its inclusion as a feature that’s apparently unique to Exchange 2016 might also puzzle some. In this case it’s probably because the amount of information returned to Outlook clients by the Exchange 2007 version of Autodiscover is much less than Exchange 2016 provides. We can therefore conclude that Outlook 2016 needs more reassurance from the server before it is willing to connect to a mailbox.

Eliminating Outlook 2007 from the set of supported clients for Exchange 2016 undermines the theory that Exchange 2016 is really the second service pack for Exchange 2013 as that (now older) server is happy to support the older client. Which is how it should be as the old should support the old. And the young? Well, they generally ignore old technology…, which is why Outlook 2007 is ignored by Exchange 2016.

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