The user will need to setup a custom filter option called X-Folder in order to sort by the X-Folder Text. This is done in the message filter rules select the down arrow the left option and add the X-Folder as the custom header. Attached is example of a X-folder filter rule. Other rules for this filter can be added at this time provide they are the same X-folder. If you have more than one X-folder such as Junk and Sent just setup separate filters for these.
Eugene
<<attachment: Filter Rules.png>>
