OST on Network Share. Supported or Not?

Essentially yes, it is supported.
As per the following Microsoft KB – the following can be extracted although earlier in the same KB it say it’s not supported but it is believe to only relate to older clients:-

Outlook 2010 or later versions hosted remotely by using Windows Server 2008 R2 or later Remote Desktop Session Host (RDSH) or Virtual Desktop Infrastructure (VDI) configuration

Outlook 2010 or later versions functionality is supported when networked .pst or .ost files are used under the following conditions:

  • A high bandwidth/low latency network connection is used.
  • There is single client access per file (one Outlook client per .pst or .ost).
  • Either Windows Server 2008 R2 or later Remote Desktop Session Host (RDSH), or Windows Server 2008 R2 or later Virtual Desktop Infrastructure (VDI) is used to run Outlook remotely.

Conclusions from this statement

  • High Bandwidth\Low Latency – would be more towards data centre provided storage
  • Assumed PST is prevented anyway in Citrix Environment, but only one mailbox OST can be accessed per User. So Outlook with 2 mailbox’s is only supporting one mailbox, others may work but essentially any performance issues will call out that only one should be attached




  1. I am currently using the same approach on OST with WIN2016 and the issue as described by Microsoft still exist. this is not a supported approach, but you are free to implemented. it works, but you will sure suffer user critics and management unhappiness.

    1. There statement says it is supported under certain conditions but yes they will ask for those elements to be proved before continuing to look at it if raised as a support call. I would recommend fslogix office365 container to overcome this as it is using block level transfer

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