version 38+ of Thunderbird was supposed to solve the problem with authenticating / connecting to gmail by adding support for OAuth v2.0. Unfortunately, I can still not send messages from any gmail account connected to Thunderbird. My account settings are as follows: IMAP server: imap.googlemail.com:993 security: SSL/TLS auth method: OAuth2 user: (full gmail address) SMTP server: smtp.googlemail.com:465 security: SSL/TLS auth method: OAuth2 user: (full gmail address) At the first connection attempt, Thunderbird presented me with the OAuth login screen, where I was asked to enter my gmail password. After this, Thunderbird shows up in the list of connected devices in the google account settings for this gmail account. So it seems the new authorization flow via OAuth 2.0 seems to work, and yet I can only read incoming email, but can't send mail. When I hit send on a message, Thunderbird very briefly shows a separate window / interface (I can't make out what it is, I assume it has to do with the oauth functionality), then hangs at "connecting to smtp.googlemail.com...' and after a while declares a timeout. Sending mail through the gmail web interface and from connected android devices works fine. I have left the setting "Allow less secure apps to access your account" set to Yes, even though Thunderbird is now connecting via OAuth 2, to eliminate that as the potential cause. Any help appreciated, I want to continue using Thunderbird with gmail.