I'm trying to use thunderbird with a google apps account. I'm using OAuth2. Here are my settings: IMPT: server: imap.googlemail.com Port: 993 connection security: SSL/TLS Authentication method: OAuth2 username: my email address SMPT: server: smpt.googlemail.com connection security: SSL/TLS Authentication method: OAuth2 port: 465 username: my email address Whenever I try to send an email, I get the following error: Sending of the message failed. An error occurred while sending mail: Outgoing server (SMTP) smpt.googlemail.com is unknown. The server may be incorrectly configured. Please verify that your Outgoing server (SMTP) settings are correct and try again. I'm not quite sure what's going wrong here: as far as I can tell I'm doing everything right. Help, please! I tried following the advice on this previous question (https://support.mozilla.org/en-US/questions/1068616) but nothing helped.