Using Thunderbird v38.2.0 (Windows) Gmail labels (aka Folders) do no auto-sync, even through "Check for new messages every ___ minutes" is set to 1min. The Synchronization & Settings settings are configured to Download every Gmail label/folder. (However, anything sent directly to the Inbox syncs without issue) If set the "When getting new messages for this account, always check this folder" option on each of the folders Thunderbird will then show a new mail count in folders, but it doesn't actually download the message until you click on the folder. I attempted changing the Advanced Config setting below, instead of manually adding it to all folders, but the issue persists. mail.server.default.check_all_folders_for_new = True Also there appears to be a large delay at times (5-10min) as to when a message is received and showing in the Gmail Web interface and when Thunderbird shows a new message (even though it is set to check every 1min). --- As an additional piece of information, if you create a folder directly underneath the Inbox in TB, (They show as label of "INBOX\FolderName" in Gmail)... then these folders sync instantly as expected without any issues. However, it is messy to have "INBOX\FolderName" littered all over the Gmail web interface, and Gmail creates labels/folders directly at the account level instead of underneath the Inbox. So, what is the difference between how Thunderbird syncs Gmail Labels and Gmail INBOX Folders? and how can we fix it so Gmail Labels function properly?