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.