User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:184.108.40.206) Gecko/20101026 Dealio Toolbar 3.1 Firefox/3.6.12 (.NET CLR 3.5.30729) Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:220.127.116.11) Gecko/20101027 Lightning/1.0b2 Thunderbird/3.1.6 The TAB order in Thunderbird with Lightning(calendar) is Email, Calendar, then any opened email messages. Upon closing any messages you're reading, the focus defaults to Calendar rather than back to Email, requiring an additional click to continue reading mail. This could be alleviated if Calendar opened as the first TAB. Reproducible: Always
This behavior is enforced by Thunderbird. Closing a tab will select the right-most tab instead of the previous tab. I think there already exists a bug for this.