After each major update there is always some people who are confused by the numbering scheme used for Thunderbird. Common question is why did the version number just jump up by 7? Thunderbird follows the Firefox ESR release numbering which means there is major release every 48 weeks or 7 regular updates of Firefox/Gecko. So, next big update will be Thunderbird 45 in March 2016. This is the tentative schedule for the next year: June 30th: Thunderbird 38.1.0 (Gecko 39) August 11th: Thunderbird 38.2.0 (Gecko 40) September 22nd: Thunderbird 38.3.0 (Gecko 41) November 3rd: Thunderbird 38.4.0 (Gecko 42) December 15th: Thunderbird 38.5.0…