After the update, the 153.0.2esr program writes about an authentication error when connecting to imap.yandex.com. Please tell me what has changed and how to fix it.

Please quote the exact error message. A screen shot of it would be helpful. Check out their article about what yandex needs in order to use "other" email clients like Thunderbird: https://yandex.com/support/yandex-360/customers/mail/en/mail-clients/others You may be running into a couple of things. If you're set up to authenticate using OAuth2 you may need to re-authenticate. To to that, - make sure that Cookies are allowed (see <Settings | Privacy & Security | Web Content | Accept cookies from sites>. - Optionally, delete any stored cookies for Gmail (see <Settings | Privacy & Security | Web Content | Accept cookies from sites | Show cookies>) and delete any saved passwords for that user name (see <Settings | Privacy & Security | Passwords | Saved Passwords>). Then quit and restart Thunderbird. When it next tries to fetch or send email, you should be prompted for your credentials as usual. - For versions 15x.x and newer, you may need to check similar things in your default web browser, that is, make sure cookies are allowed and remove any existing cookies related to Gmail. (This is my understanding - I haven't had to do this yet.) ------------------ The above web page also mentions that you may need to create an app password. Most providers require that you need to use ''either'' OAuth2 OR an app password, but they may require both - we have no way of knowing.