Windows Live Mail automatically detect what language you’re using and spellcheck in that language. However, if you often send mail in different languages you can use a Windows tool “Language Bar” that allows you to easily change languages in Windows, without having mess around with your spellchecking settings. Whenever you do this, Windows Live Mail will pick up that change in a couple seconds and switch the language being used to spellcheck the email you’re composing. Here’s some information about the Language Bar and how you can use it to switch languages:
Also, if you’d like, you can turn off the language detection feature and explicitly set the language being used when spellchecking. To do this, open the options dialog in Windows Live Mail by clicking on “Options” here:
In the Option dialog that pops up, select the “Spelling” tab. The option you want to turn off is “Check spelling in current input language” – uncheck that check box. Then you can select a new default language in the Languages list – simply select the language you want to spellcheck in, then hit the “Set Default” button to make it your spellchecking language. If the language wasn’t installed, you’ll need to click the “Install” button before you click the “Set Default” button – that’ll download the language you want from Microsoft’s servers.