'Thank you all" isn't actually correct; the all is added as an afterthought to clarify the person is thanking everyone. It would be more correct to …
首先，來認識一下這些常使用於英文書信中的基本用語： 正式性程度等級 ★ : Thanks for all your help. 舉例來說，這邊可以用在例如感謝同事的協助你完成工作 …
“ Thanks to all”, “Thank you everyone” and “Thanks all” – all these are correct. But they are different in the case of situation and audience. …
更多内容请点击：【信件英文】實用商務英文！教你如何在郵件中表達感謝