wso2 send email MIME encoded-word header "from" - email

Question

I have json messages like this:
{
"subject": "Enchanté"
"sender_name": "Rémi"
"sender_email" "foo#bar.com"
}
I'm using wso2 5.0.0 to send an email using MailTransportSender with something like this:
<property name="Subject" expression="json-eval($.subject)" scope="transport"/>
<property name="From" expression="fn:concat(json-eval($.sender_name), ' <', json-eval($.sender_email),'>')" scope="transport"/>
The smtp email is
From: Rémi <foo#bar.com>
Subject: =?UTF8?Q?Enchant=C3=A9?=
Note that wso2 correctly encodes the Subject: but not the FROM: . It should be :
From: =?UTF8?Q?R=C3=A9mi?= <foo#bar.com>
How to make wso2esb encode the sender_name as well (rfc2047) ?