Many years ago, Gmail changed their folder structure so some of the IMAP settings tutorials are not correct anymore. Since Windows Live Mail (WLM) auto-configures Gmail, the special folders are automatically determined and they cannot be specified. Please leave Root folder path alone like this:
Basically Gmail decided with the exception of Inbox, which stays at root, all “System labels” goes under the subfolder [Gmail]. However user-created labels (simply called “Labels“) stay at root folder level. For example, I have a user folder called Save enabled for IMAP, the folder tree with the Gmail account looks like this:
Because you cannot specify where the Trash folder is, delete button really mean delete (to a recycle bin that’s purged in 30 days), not archive to a folder.
Also because Gmail is smart enough to save a copy in your [Gmail]/Sent Mail folder if you use their SMTP (out-going mail) server, the “Save copy of sent message in ‘Sent Items’ folder” setting on Windows Live Mail is irrelevant: you cannot choose not to save it.
And yes, I tried it checking this (for other non-Gmail accounts), and confirmed that Gmail is smart enough to save one copy (not one from the SMTP and one executed by the client).
So here’s a summary:
Gmail automatically configures and dictates IMAP’s special folders. You have no choice
No special folder choice means you cannot reroute ‘delete’ to mean archive/move
If you use Gmail’s SMTP server (likely), it will save a copy of outgoing mail to [Gmail]/Sent Mail folder. You cannot turn this off.
“Save copy of sent message in the ‘Sent Items’ folder‘ is irrelevant if you use Gmail’s SMTP server. It will correctly save only one copy of the sent mail.