Odoo sends mail with base64 encoding when you look at the mail sourcecode in a mailclient. Is it possible to disable base64?

--===============6626283485342417593==
Content-Type: multipart/alternative;
 boundary="===============4756281152447456149=="
MIME-Version: 1.0

--===============4756281152447456149==
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: base64

dHJlc3QKCk1ldCB2cmllbmRlbGlqa2UgZ3JvZXQsCgpPcGVud29yeAoKCgo=

--===============4756281152447456149==
Content-Type: text/html; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: base64

PGJhc2UgaHJlZj0naHR0cHM6Ly93d3cub3BlbndvcngubmwnPgo8cD50cmVzdDwvcD4KCjxwPk1l
dCB2cmllbmRlbGlqa2UgZ3JvZXQsPC9wPgoKPHA+T3Blbndvcng8L3A+Cgo8cD48aW1nIGFsdD0i
IiBzcmM9ImRhdGE6aW1hZ2UvanBlZztiYXNlNjQsLzlqLzRBQVFTa1pKUmdBQkFRRUFTQUJJQUFE