mail in other language

1. From the Dock, choose System Preferences;
2. Choose Keyboard;
3. Choose Input Sources;
4. Check the box to Show Input menu in menu bar, then click the Plus sign at the bottom left to bring up the languages menu:
5. Select the desired language(Dutch)(English) and click Add;

FredEnsel wrote:

I am a dutchman, but I want to mail in the english language. How can I switch to another language?

What exactly are you talking about? Are you having trouble typing in English? Do you need some kind of language translation? Is the spellcheck not right? Perhaps post a screen shot to show us what the problem is.