Encoded Subjects

Hi.
I have problems to send emails with non US characters with WebDAV.

I use a XMLHTTP object with "message/rfc821" header, something like this:

    Set xmlReq = New XMLHTTP
   xmlReq.open "PUT", strURL, False, strUser, strPassWord
   xmlReq.setRequestHeader "Content-Type", "message/rfc821"
   xmlReq.setRequestHeader "Saveinsent", "f"
   xmlReq.Send strMailData

The subject of the mail, inside the strMailData string is :
Subject: El veloz murciélago hindú

The mail is send OK but the subject is received bad, the client receive
Subject: =?iso-8859-1?Q?El_veloz_murci=C3=A9lago_hind=C3=BA?=
Instead of:
Subject: =?iso-8859-1?Q?El_vel=F3z_murci=E9lago_hid=FA?=

I don't know why OWA encode two times the subject before send the mail
to the receiver. ¿Any help?

Un saludo
Carlos Garcés