Gmail imposes bandwidth limits as explained here https://support.google.com/a/answer/1071518?hl=en Your screenshot shows Thunderbird in the process of downloading a large number of messages. The only thing you can do, is limit data transfer between Thunderbird and Gmail. By default, Thunderbird will synchronize/download ALL messages in ALL subscribed IMAP folders. That will '''quickly hit the bandwidth limit'''. In Account Settings, however, you can choose which IMAP folders Thunderbird should synchronize, and also further limit the age and/or size of messages that it should download. That's what you should do. [[Refer to Thunderbird and Gmail]] and [[IMAP Synchronization]] for details.