Exchange login popup

Hello,
i am trying switch to em client but it is faililing to login exchange.
Using wizard i have added exchnage type mail account, next i filled up correct mail, user name (domain\login) and password. EMC found server and configure, then save. Then EMC ask me for password. Strange is that used username in showed form was without domain name. Why? I have correct it to format domain\login, reenter pass and it is showing again and again. I have tries different login format also: login@domain.cz …
Nothing help. Server has not public signed certificate, it has cert signet by its own CA.
In debug log is not any error message, only trace where EMC tries send xml request to load folder. Contact were partially loaded. Mail nothing.
Using owa or outlook connectoin works fine.
Thank you for help