Hi darkan9el,
By "upgrade" it sounds like your clients email hosting provider migrated their email to a new server and/or changed the IMAP server that is used for getting their email.
Either way, if not handled correctly, the server change -will- result in a very confused Microsoft Outlook.
If your client has all of their email stored on the server, and only gets it with IMAP, and none of it is stored locally on the computer, the best action is to delete the profile in Microsoft Outlook and then recreate their connection settings.
Only changing the settings within an existing profile won't fix the problem. This is because each IMAP server has it's own way of tracking subscribed folders, message UID's, etc and if that wasn't done correctly the best thing to do is "start over".
If Roundcube is using IMAP deleting an email there should result in it also "deleting" from Microsoft Outlook.
Changing IMAP subscription settings doesn't delete email it only affects which folders may be seen by a mail program.
Your client should not lose any email, but it's still a good idea to backup their current PST file just in case so you can reattach it to Outlook later if needed for any reason.
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