https://english.stackexchange.com/questions/332/which-expressions-can-be-used-to-close-an-email
https://www.english-at-home.com/business/how-to-start-and-end-a-business-english-letter-or-email/
https://www.vestner.de/1077f7/1c0c4d-informal-email-phrases
http://languagelearningbase.com/257/how-to-end-emails
