Public Folder migration request error creating the Public Folder Hierarchy – “Property Expression [property name] isn’t valid”

To migrate your legacy public folders to Exchange 2013, you should follow all the steps described on the official Microsoft article.

Step 2 of the article mentioned above, helps you prevent errors related to the public folder name, such as having a “\”. But this blog post is related with something which is not covered by the article, and that can make your public folder migration request throw an error: Invalid alias on mail enabled public folders.

So as described on step 5 of the article, you start your migration request by running the following cmdlet:



New-PublicFolderMigrationRequest -SourceDatabase (Get-PublicFolderDatabase -Server <Source server name>) -CSVData (Get-Content <Folder to mailbox map path> -Encoding Byte) -BadItemLimit 200 -acceptlargedataloss -largeitemlimit 200

Note: On the above cmdlet i used both the baditemlimit and largeitemlimit set to 200, because i knew that my public folders had a significant number of both bad and large items. If that is not your case keep the bad and the large item limits to a minimum if at all specified.

Once the public folder migration starts you can run the following cmdlet to see the progress. If you have invalid alias on the mail enabled public folders, the migration request will fail at 10%, when creating the Public Folder Hierarchy:




To get the details of the error you need to run the same cmdlet, but with the “|fl” at the end, as shown below:



Get-PublicFolderMigrationRequest |Get-PublicFolderMigrationRequestStatistics |fl

On the details you can see the following:


On the screenshot above you can see that the mail enabled public folder “Accountancy Properties” has an invalid alias, and that is because you cannot have spaces (and other characters as shown above) on the alias. So the next step would be to fix all mail enabled public folders with invalid aliases.

Go to your Exchange Management Shell and run a cmdlet that will list all the mail enabled public folders with spaces. Of course some other mail enabled public folders can have other problems, but in my case it was only the spaces. If you have other problems besides spaces you can adapt the “where-object” filtering from the cmdlet below, to those characters. Also to get an output of all the mail enabled public folders with issues, you can run the following cmdled and see which public folders throw a warning:


All the mail enabled public folders will throw a warning on the output, but of course we need to have a list of only the ones with problems to resolve the issue quicker. So to have a list with all the ones with spaces, and export it into a csv file, run the following cmdlet:






Get-MailPublicFolder | Where-Object {$_.Alias -like "* *"} | Select-Object alias, identity |export-csv [CSV file path and name]

Note: On the cmdlet above, if you’re problem is not limited to spaces on the alias, you can change the where-object filtering to try and find other invalid characters.

Once that is done you will get a csv file with all the mail enabled public folders with invalid aliases, as shown below:




Having that information you can now fix all the mail enabled public folders. You have two ways of doing it:

Option 1:

You can open your Exchange Management Console, go to tools and then open the Public folder Management Console. Expand the Public Folder tree and go to the properties of each public folder with problems. On the “Exchange General” tab change the alias and apply, as shown below.






Option 2:

You can use the Exchange Management Shell, and run the following cmdlet:






Get-MailPublicFolder [Public Folder Name] |Set-MailPublicFolder -Alias [PublicFolderAlias]

Once you set the valid alias you problem is solved for that specific public folder. You might be thinking “how can i automate this for the dozens or hundreds of public folders i have with issues?”. Well the answer is you should use that csv file you exported with all the public folders, insert a column with valid aliases, build a script that reads from the csv file and run it from the Exchange Management Shell to have all your folders fixed in one go. In my case i had a low number of folders with issues, so i haven’t built the script. I am planning to build 2 scripts, one to export public folders with issues and another one to use that exported file and fix those issues, but at the moment i don’t have it. Feel free to ping me an e-mail or comment if you’re interested on the script and i can find some time to build it. It should be a fairly simple script. Or feel free to have a go on doing that.

But back to the issue. Once you have all your mail public folders with valid aliases, i recommend that you remove the current public folder migration request and create a new one. To do that run the sequence of cmdlets shown below:







To see the current failed request:

To delete the current failed request:
Get-PublicFolderMigrationRequest |Remove-PublicFolderMigrationRequest
To create a new request:
New-PublicFolderMigrationRequest -SourceDatabase (Get-PublicFolderDatabase -Server <Source server name>) -CSVData (Get-Content <Folder to mailbox map path> -Encoding Byte) -BadItemLimit 200 -acceptlargedataloss -largeitemlimit 200

Finally after the new request is created, you can see that now the migration is ongoing and went past the Public Folder Hierarchy creation without issues.




Problem solved and happy migration! 🙂








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