I am using Mail app in Windows 10 to sync with my Gmail account via IMAP. When I add the account, Mail automatically creates several folders like Inbox, Sent Mail, All Mail, Drafts, Trash, as well as Outbox. Gmail does not have Outbox for some time now.
So, I get this warning about IMAP settings
Of course, I followed the instructions and made sure all my folders are IMAP accessible. I wonder if the warning is related to the fact Outbox does not exist in Gmail.