icedove corrupts accented letters

[Frederik AA de Jonge <fredjnm@yahoo.com>]

since upgrading to stretch
all emails sent from icedove
have their accented letters corrupted

email with text like this
problema com acentos
a??e??i??????
????o
altera????o

is received like this
problema com acentos
a??e??i??????
????o
altera????o

all accented letters become '??'
irrespective of whether is ask to send plain mail or html mail
encoding = utf-8

this error makes icedove unusable for me

any thoughts?

related to email provider = yahoo?

regards

frederik