Hi !
since I upgraded to Tails 2.4~rc1, I got a lot of trouble sending mails
with icedove, using boum's smtp, and we get a report from someone having
the same issue with riseup.
did you heard anything about that here ?
anyway, I reopened
https://labs.riseup.net/code/issues/10933 since it
seems to be the same thing, the error is still the same "unknown reason"
cheers.