In Exchange Server 2010 the administrator can choose to block non-cached mode Outlook clients from connecting to Exchange.

Blocking non-cached mode Outlook connections is useful in some scenarios, such as:

  • Reducing server workload to get better perform from server and disk resources
  • Reducing network bandwidth utilization for remotely connecting users

Online Outlook clients can be blocked on a per-user basis using the Set-CASMailbox command. For example:

[PS] C:\>Set-CASMailbox kelly.chatir -MAPIBlockOutlookNonCachedMode $true

You can see the setting for a user by running Get-CASMailbox.

[PS] C:\>Get-CASMailbox kelly.chatir | fl name,mapi*

Name                          : Kelly.Chatir
MAPIEnabled                   : True
MAPIBlockOutlookNonCachedMode : True
MAPIBlockOutlookVersions      :
MAPIBlockOutlookRpcHttp       : False

You can also apply the change to multiple users at once. For example, to block non-cached mode for all users in the Branch Office location:

[PS] C:\>get-mailbox | where {$_.office -eq "Branch Office"} | set-casmailbox -MAPIBlockOutlookNonCachedMode $true

To locate all mailbox users that have non-cached mode blocked run this command:

[PS] C:\>get-casmailbox | where {$_.mapiblockoutlooknoncachedmode -eq "True"}

Name                 ActiveSyncEnabled OWAEnabled           PopEnabled          ImapEnabled         MapiEnabled
----                 ----------------- ----------           ----------          -----------         -----------
Aisha.Bhari          True              True                 True                True                True
Andy.Crossley        True              True                 True                True                True
Carol.Tubby          True              True                 True                True                True
David.Marriott       True              True                 True                True                True
Dukh.Morgan          True              True                 True                True                True
Georgie.Jeyapragasam True              True                 True                True                True
Hilary.Shortt        True              True                 True                True                True
Jennifer.Sparks      True              True                 True                True                True
Judith.Woodland      True              True                 True                True                True
Kelly.Chatir         True              True                 True                True                True
Lorraine.Rideout     True              True                 True                True                True
Marcia.Barnett       True              True                 True                True                True
Meena.Salt           True              True                 True                True                True
Neville.Sherwin      True              True                 True                True                True
Pauline.Taylor       True              True                 True                True                True
Robert.Henderson     True              True                 True                True                True
Sharnjit.Mcilroy     True              True                 True                True                True
Suki.Murray          True              True                 True                True                True
Valerie.Andrews      True              True                 True                True                True
Wendy.Fyson          True              True                 True                True                True

Finally, to locate all users who are not blocked from using Outlook in non-cached mode, you would run the same command but check for “False” instead.

[PS] C:\>get-casmailbox | where {$_.mapiblockoutlooknoncachedmode -eq "False"}

About the Author

Paul Cunningham

Paul is a former Microsoft MVP for Office Apps and Services. He works as a consultant, writer, and trainer specializing in Office 365 and Exchange Server. Paul no longer writes for Practical365.com.

Comments

  1. Robert

    Interesting. We have several hundred hyper-v test machines and actually want the opposite behavior – we don’t want testers to use cache mode as waste valuable VM machine hard disk space.

      1. Steve Noto

        How can I stop users form using cache mode? Cache mode works well, but we have users logging into multiple machines and downloading their email to each machine. Some PC are older and limited disk space.

      2. Paul Cunningham

        Hi Steve, there are group policies available for disabling cached mode.

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