Spelling language: how to choose it on a per-message basis

I usually write eMail in two languages.

However, I cannot figure out how to switch language for a new mail message. I mean: English is the default language, but, when I write a message in the second language, I cannot specify which language should be used, English stays.

Is it possible with em client?

When you are composing a new message, right-click in the message body and choose the spell check language.