If you are using Outlook 2010, you can define your own style and select your formatting you want, in the Format options there is one option for Language, here you can specify the language and specify whether you want spell checker to ignore the text with this style.
With this style you can now paste the code as text and select your new style. Outlook will not correct the text and will not perform the spell check on it.
Below is the summary of the style I have defined for emailing the code snippets.
Do not check spelling or grammar, Border:
Box: (Single solid line, Orange, 0.5 pt Line width)
Pattern: Clear (Custom Color(RGB(253,253,217))), Style: Linked, Automatically update, Quick Style
Based on: HTML Preformatted