emacs complains about encoding?

[David Belohrad]

Dear all,

i've just yesterday pulled from git recent version of notmuch and
started to use it. With respect to previous version (~2months old?) I
have now problem, that when I receive from somebody an email using
'whatever' (understood uknown) encoding, the email is in emacs displayed
correctly. When I want to answer however to this, all the characters
(like czech accented letters) are 'thrashed' in the original mail. It
seems like the mail buffer does not use utf encoding or what.

When I try to send such email, I'm asked about what to do with those
characters and what charset to use etcetc. bit annoying. 

Could someone give me a hint what to change to make it again running?

thanks  a lot

d.