As part of a recent domain migration, I had to convert a number of linked mailboxes to standard “user” mailboxes. The well known method for converting linked mailboxes is to disconnect the mailbox, change the type and then reconnect. This is fine you just have a few linked mailboxes to deal with, but not if you have a whole lot.
I found a great script written by Georg Hinterhofer that seemed to be just what I needed. When I tried the script it failed because the values for $AclContainingAEA show as being in the form <domain>\<user>. Normally, this would be ok, but in my case the user objects involved had been migrated with SIDHistory. This mean that the $AclContainingAEA values were interpreted by the script as being from the target domain, when in fact behind the scenes the values corresponded to the SID from the source domain. It meant I had to do a little trickery to get the script to work for my scenario. My update to the script is here: convertlinkedmailbox.txt
Georg wrote the script for Exchange 2007, but it works equally well for Exchange 2010.