[2] Thunderbird — メールをもっと簡単に。 — Mozilla (2018-04-04 19:13:07 +09:00) https://www.mozilla.org/ja/thunderbird/

[1] Thunderbird’s Future Home | The Mozilla Thunderbird Blog (2017-05-14 13:00:14 +09:00) https://blog.mozilla.org/thunderbird/2017/05/thunderbirds-future-home/

[3] Mozilla Thunderbird - Wikipedia (2018-04-03 00:43:40 +09:00) https://ja.wikipedia.org/wiki/Mozilla_Thunderbird