Yes, the system supports sending emails in foreign languages. Our email designer, Campaigns, Templates as well as some contact data fields (unicode text fields) all support 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 --> Configure Fields and check the "Field Types" column.
This includes support for Mandarin.