[Dovecot] authenticate plain and utf-8 with special chars

Hi,

I experienced some problems with authenticate.

seems like the mail clients like thunderbird send their base64 string in ISO- encoding, which doesnt work on my dovecot setup if there are some Umlauts

I am not able to login as "ömer" for example

If I authenticate from telnet with an base64 encoded utf-8 string like 'echo -en "\0ömer\0Start12" |base64' everything works fine

-dovecot 2.1.7 -userdb is an openldap which queries an windows AD so results are in utf8, I think.

any clues at which point to fix this are welcome ;)