This is due to how Exchange (Outlook) or your email application handles foreign characters.
By default the character code set used is UTF-8. However if foreign characters are not being displayed properly then you can change this to something else by adding the following comment anywhere on your source template AFTER the first line – if you add it as the first line it will be removed.
Change the character set code as appropriate. The above code set for example works fine for French accents (Western character set). A full code set can be found at http://webcheatsheet.com/html/character_sets_list.php.
If that does not work then for test purposes, send the email to a Gmail account and view it in Gmail to see how it is displayed. If that works fine then you will need to check your Exchange settings and updates and AV settings/updates.
If license emails have been working fine before then see http://social.technet.microsoft.com/Forums/exchange/en-US/d38d6047-912e-4153-80e2-4968d8b5eefa/html-messages-mishandled-exchange-2010-sp1-outlook-2007-sp2?forum=exchangesvrclientslegacy.