Unable to open PST file "filepath". Error details: Access to the path "filepath" is denied.
When examining the PST file you notice that your account does indeed have permissions to access the PST file on your local computer. Why is this error occurring?
This is because the Mailbox Replication Server (MRS) is running as LocalSystem it can’t access a network share. By adding the Exchange Trusted Subsystem group to the share permissions you will give the LocalSystem account and therefore MRS access to the share.
To ensure this works for all PST files on a machine in any share, you can simply add "Exchange Trusted Subsystem" to the local Administrators group.