Are you trying export mailbox into a PST (or import PST into mailbox)? And you are stuck here with this message.
Unable to open PST file ‘\\FileServer\Share\JohnDoe.pst’. Error details: Access to the path ‘\\FileServer\Share\JohnDoe.pst’ is denied.; Microsoft.Exchange.MailboxReplicationService.RemotePermanentException: Access to the path ‘\\FileServer\Share\JohnDoe.pst’ is denied.
There is a simple explanation and solution.
Mailbox Import and Export process is handled by Exchange MRS component. If you check the Microsoft Exchange Mailbox Replication service properties, you will see the service is running under “Local System account”. That means the file share location you specified in the New-MailboxExportRequest or New-MailboxImportRequest doesn’t have permissions to Exchange Trusted Subsystem.
The solutions as you guessed enable Read/Write permissions to Exchange Trusted Subsystem for the network location (NTFS and Share permissions). Try again.
If you haven’t got the whole point of this setup, here it is. You should have create a special share with locked down permissions to export mailboxes.
Anand, the Architect 
That was it! Thanks!
This fixed my issue. Thank you!
You can also get this error if you create the export share on the mail server itself. By adding the share on another server and ensuring Exchange Trusted Subsystem has access worked. Thanks
Still valid; Exchange 2013 CU8. Thanks. Our problem was we created the share on the MBX server; created the share somewhere else and it worked. Thanks.
Thank you Stu….that was my problem!!!
I still had an issue after adding in the Exchange Trusted Subsystem into the NTFS and SHARE permissions. What worked for me is when I also added SYSTEM. I found this object in all of the built-in Exchange shares like Address, ExchangeOAB and GroupMetrics.
Adding Exchange Trusted Subsystem wasnt enough… Glen’s solution worked for me!
Also note that hidden admin shares e.g. C$ don’t seem to work with this cmdlet — a new share with the correct NTFS / share permissions are needed.
thanks stu, that was also my issue… thanks for your help guys
thank you that worked
Awesome!!! Worked a charm. Tried so much other things I’d almost given up.
THANK-YOU! Was pulling my hair out trying to get PowerShell to archive Exchange 2010 PSTs to a NAS share (AD aware). Once I granted access to Exchange Trusted Subsystem…. all good. Now totally bald, but at least I can archive…
Still relevant in 2017, thanks for taking the time to write this.
Still relevant in 2018 too. Thanks for leaving this old, but very helpful information up!
Unable to save it on an actual server, solved it by setting up a share in a Windows 10 PC instead of a Windows Server.
Not needed to add Exchange Trusted Subsystem or other. Only “Authenticated Users”, “System”, “mypcname\Adminstrators” and “mypcname\Users” were added in security.
“Authenticated Users”, “System”, “mypcname\Adminstrators” and “mypcname\Users” may lead to security breach. Just Add provide access only to “System” in Share and permission tap.
Still relevant in 2019, thanks for the post and for leaving for me to find in my hour of need.
Great. Have been stuck with this error for long. Your help is greatly appreciated. Thank you.