[horde] Need help with encoding

[San]

My received and sent e-mail in HTML does not recognize the accent in
Portuguese character, like ã,õ,ç and so on, since I instaled Horde 4 with
CenOS 5.6 and PHP 5.3. I changed the encoding (UTF-8 and ISO-8859-1) in the
browser, Apache, PHP and in the OS, but nothing does it's work.

Here is the example of message received and sent in HTML by Horde:
-----------------------------------------------------
teste de acentuação html
-----------------------------------------------------

Installation:

pear list -c horde
 ...
 horde                    4.0.8
 imp                       5.0.10
 ...

php-5.3.8-1.w5