I am trying to use this class. It works fine, and I'm receiving the email, but it doesn't work with Arabic characters. How can I solve this problem?
If you used the SQL provided by the library author without modification, that's probably the source of your problem. The table definitions given exclude all character set information. This means that MySQL will use whatever default character set it's been configured for. Unfortunately the default configuration uses one of the Latin variants by default (and then dares to call it Swedish).
You will need to change the character set for the tables, after which you might get better results. You will almost certainly need to set character sets on each table and on the connection itself.
Also, you might want to find another library. The code given is clearly ancient and is poorly documented. It doesn't seem to go through any steps to ensure that character sets are treated properly, though it's far more likely that the database is more at fault here than not. (Worse, it uses addslashes for SQL escaping, which is basically the most utterly horrible level of protection possible against SQL Injection.)