I found the problem :
the header of the HTML email was with an Encoding = quoted-printable
the header of the Text email was with an Encoding = 8bit
=> I’ve forced the HTML email to be with header Encoding=8bit
I found the problem :
the header of the HTML email was with an Encoding = quoted-printable
the header of the Text email was with an Encoding = 8bit
=> I’ve forced the HTML email to be with header Encoding=8bit