[Dovecot] French characters from 2.0.x to 2.1.3

[Frank Bonnet]

Hello

Maybe it's a coincidence but it "seems"
since I upgrade from 2.0.18 to 2.1.3
that some French characters ( a with accents by example )
are not well displayed anymore  using thunderbird and are
replaced by a "?" character

Thanks for any info