Hello, a few days ago, I started having problems with one of my Gmail accounts. I use Thunderbird and have several different Gmail addresses assigned to it. A few days ago, one of the mailboxes stopped working properly, i.e., messages download very slowly, it's impossible to mark a message as read (and if it happens after a few minutes, the message is still unread on the mail.google.com/mail page). I suspect a synchronization problem with Thunderbird, because everything arrives instantly directly on the Gmail page. I've been using this mailbox for over two years and never had any problems. The mailbox was used normally, i.e., dozens of incoming messages a day and a few outgoing messages, without large attachments. The settings weren't changed either -> imap.gmail.com / 993 ; SSL/TLS OAuth2 ; smtp.gmail.com / 465 ; SSL/TLS OAuth2. I tried adding the mailbox again, but the same thing is happening today. I tried different settings in Thunderbird and in Google settings, but nothing helped. Does anyone have any ideas why this is happening? I have to use the web version of Gmail, because nothing can be done on Thunderbird. to do it efficiently - read or reply to a message.