Yes, the system supports sending emails in foreign languages. Our Editor, Campaigns, and Unicode text fields support foreign characters.
It's important to note that if you plan to use merge tags, you may have some restrictions on which fields you can use depending on the types of characters needed. For character based foreign languages, you will need to use Unicode text fields, not general text fields.
Looking Up Field Types:
To determine which fields are unicode vs general text fields, visit Contacts --> Configuration --> Custom Fields and check the "Field Types" column.