I'm trying to help someone migrate to Thunderbird. They have a BT Internet email account. After entering the settings, incoming mail works successfully, but outgoing mail fails every time with an error. The error is Login to server mail.btinternet.com with username [email protected] failed. Followed by Sending of the message failed. Unable to authenticate to Outgoing server (SMTP) mail.btinternet.com. Please check the password and verify the 'Authentication method' in 'Account Settings | Outgoing server (SMTP)'. BT says the settings are: Outgoing Mail Server: '''mail.btinternet.com''' Port: '''465''' (this may not be automatically populated on selecting SSL, so you'll need to check) SSL Encryption: Enabled (but not STARTTLS) '''** I have used the SSL/TLS setting''' Authentication: PLAIN ** I have selected '''normal password''' Username: your email address including the @btinternet or @btopenworld.com part Password: your btinternet or btopenworld password Have I missed something obvious? It's driving me NUTS!