XenApp/XenDesktop + Office 365: Citrix’s data on optimal user experience

Jo Harder looks at Citrix’s data on how to get a high-quality user experience from Outlook on XenApp/XenDesktop when using Office 365.

While there has been much speculation about how to provide the best user experience for Office 365, the facts and figures tell all. Citrix recently published the results of some testing that they performed, comparing Exchange Online performance in on-premises deployments of XenApp to Azure-based deployments of XenApp. Jo Harder, who conferred on the project, walks us through Citrix Engineering test results.

Office 365

Large organizations and small ones are deploying Office 365 in rapid succession. Oftentimes, the decision to adopt Office 365 is made in the corner office, and the Citrix administrator is merely advised that the change is coming—and soon.

If the default configuration is used, wherein XenApp/XenDesktop is located on premises in conjunction with Exchange Online, the user must wait for each and every transaction to cross the wire. The resulting user experience is terrible, as Outlook is barely usable.

There have been numerous articles and discussions related to the best way to implement Office 365 with Citrix XenApp/XenDesktop. When the Citrix resources remain in the data center, enabling Cached Exchange Mode provides the best user experience. This can be enabled via Group Policy or individually within Outlook user account settings (File > Info > Account Settings > Account Settings > Change > Server Settings > Offline Settings).

However, a key use case to consider is the deployment of XenApp/XenDesktop in Azure.

User Experience Data

The user experience is paramount, so what is the precise benefit of the various options from the perspective of the user? Citrix put this and other scenarios into their labs and produced an awesome white paper entitled, Deployment Guide | Microsoft Office 365 for Citrix XenApp and XenDesktop 7.x (PDF).

A little background on the project: Within Citrix, John D’Agati and his team undertook the effort to determine the best way to implement Office 365. Chris Burke did the heavy lifting in the lab and consolidated the results, Kurt Moody added a splash of his expertise and mashed it into a usable document, and I provided some real-world guidance and reviews in our weekly meetings.

In the project, numerous scenarios were tested including Exchange Online vs. caching, reading vs. sending mail, sending various size attachments, and data center vs. Azure deployment.

The white paper contains empirical data validating the following:

  • When XenApp is hosted in Azure, no additional configuration or storage are required, and the user experience is robust.
  • When XenApp is hosted in the data center, using cached mode is the only way to go; however, additional configuration is required and sufficient storage must be allocated. 

If you are planning to deploy XenApp/XenDesktop in Azure, this might be the extra nudge that your organization needs to make it happen sooner than later.

Of course, Citrix’ goal is providing administrators with knowledge about the best user experience for XenApp/XenDesktop and Office 365. Citrix has committed to updating this white paper as new technologies are released, and at least one Citrix Ready partner solution will be included in the next round of testing.

XenApp/XenDesktop Onsite + Office 365/Exchange Online

If you are planning to keep XenApp/XenDesktop onsite, a few ‘gotchas’ to keep in mind:

  • Exchange Online: The Exchange Online user experience is quantified in the document and is H-O-R-R-I-B-L-E no matter how you slice and dice it.
  • Cache Size: It’s not necessary to set the cache size tremendously large. A one-month cache facilitates the improved user experience, and slowness is only noticed when searching is performed because of additional Exchange Online communications. It also keeps storage requirements as low as possible.
  • Cache Size Storage: Your user mailbox size will likely increase as you move to Azure, i.e., 50 Gb. That means that users that had previously kept their mailboxes trimmed to only a few Gb no longer have any incentive to do so. As a result, a one- or three-month cache size based on your current calculations may be incorrect, and you’ll need to plan your storage requirements accordingly.
  • AppData Folder: The user’s OST file is stored in the AppData folder. If the user profile/folder redirection solution that you’re using isn’t configured to store that OST file and you enable cached mode, the OST file will be downloaded as part of each Citrix session initiation. Not only does that mean that Outlook will be slow to launch, but your network will likely be saturated during morning logons.


The referenced white paper now provides some empirical data related to the user experience for Office 365/Exchange Online with XenApp/XenDesktop. It can serve as a guide for Citrix administrators as they seek to provide the best user experience for Office 365 deployments.

Dig Deeper on Citrix virtual desktops