One person (business partner from UK) sent me an e-mail starting like this :

"Hello Dominique
Trust you well.
....
..."

Is "Trust you well" slang ?
Is "Trust you well" something we can use with quiet everybody when sending an e-mail ? 用 英語 (美國) 要怎麼說？

查看翻譯

It's a misspelling of "I trust you're well."
"I trust you're well." = "J'espère que vous allez bien."
It's not slang, but it's also not common in U.S. English, where it would sound formal or affected. If your U.K. partner uses it, then feel free to respond in kind.