[otrs] wrong encoding after update to v2.2.3

Hi, I have a big problem - just migrated to v2.2.3 running in utf-8. Now, mails sent out are iso-encoded, and the mail-header claims the mail to be utf-8-encoded. So Umlauts are displayed wrong. If I manually set my mail-client to ISO, the mail is displayed correct. This is new since v2.2.x, didn't had problems in v2.1.x Urgend help necessary. Bye, Alex