We hvae so many words or phrases that we could use when you end letter or email such as sincerely, best regards, truly yours,..... I'm looking for some casual, not pretentious, warm but not too sweet words that I can use to someone who I don't know well but like to send a short thank you note. As a non-native speaker, sincerely sounds too formal, best regards sounds also formal, tryly yours sounds too sweet,... I don't know why though. Thanks in advance!